Treaty Withdrawals and Security Realignments: Potential Impact of U.S. Disengagement in Asia

May 19, 2025

By Syed Munir Khasru

Indo-Pacific, Security

The prospect of U.S. disengagement from its security commitments in Asia under a second Trump administration presents a watershed moment for regional stability and international relations.^[1] For decades, the United States has functioned as the primary security guarantor in the Indo-Pacific region, establishing and maintaining alliances that have underpinned an era of relative peace and unprecedented economic growth.^[2] This complex web of security arrangements has created a status quo that, while imperfect, has prevented major power conflicts and facilitated regional cooperation. However, a renewed emphasis on unilateralism coupled with an “America First” doctrine could fundamentally alter this established order, potentially leading to withdrawal from key defense treaties and triggering a comprehensive reshaping of the geopolitical landscape.

The Strategic Context of Indo-Pacific Security

The Indo-Pacific region remains the epicenter of global power competition in the 21^st century, hosting multiple flashpoints that could erupt into conflict without careful management.^[3] The People’s Republic of China’s growing assertiveness in the South China Sea, including island-building activities and territorial claims that conflict with international law, represents a direct challenge to the rules-based international order.^[4] In the Taiwan Strait, increasing military pressure and diplomatic isolation of Taiwan creates persistent tension that could escalate into armed conflict.^[5]The Democratic People’s Republic of Korea’s (DPRK, North Korea) nuclear weapons program and unpredictable leadership continue to threaten regional stability, while unresolved territorial disputes between various nations maintain a constant undercurrent of potential conflict.^[6]

In this volatile environment, U.S. treaty alliances with Japan, South Korea, the Philippines, Australia, and Thailand have functioned as significant deterrents against aggression and unilateral actions that could destabilize the region.^[7] These alliances provide not only military support but also diplomatic coherence that helps maintain predictable interstate relations. However, President Trump’s deep skepticism toward multilateral agreements and persistent concerns about equitable burden-sharing could place these arrangements in jeopardy during a second administration.^[8] His previous statements questioning the value of these alliances and suggesting allies should pay substantially more for U.S. protection indicate a transactional view of international security that diverges from decades of American foreign policy consensus.^[9]

A withdrawal from even one major security treaty would send profound shockwaves through the region, creating ripple effects that would be difficult to predict or contain. The absence of firm U.S. security commitments would likely embolden regional powers with revisionist agendas, destabilize long-standing partnerships, and prompt countries to pursue alternative security arrangements out of necessity rather than choice.^[10] The potential ramifications include heightened militarization across the region, increased prospects for nuclear proliferation as nations seek independent deterrence capabilities, and unpredictable shifts in regional alignments that could fundamentally alter the balance of power.

Low-Probability, High-Impact Events

While traditional security concerns dominate strategic planning, unforeseen events—commonly referred to as “Black Swan” occurrences—could rapidly transform the region’s dynamics. These low-probability but high-impact scenarios warrant serious consideration in any comprehensive assessment of regional security, particularly in the context of potential U.S. disengagement.

North Korea’s Nuclear Sabre Rattling and Potential Fallout

A catastrophic nuclear attack and/or accident emanating from North Korea represents one of the most alarming potential scenarios in the region.^[11] Whether resulting from technical failure, human error, or deliberate action during a crisis, such an event could devastate the Korean Peninsula and surrounding regions.^[12] Radiation fallout would likely trigger mass evacuations, create unprecedented humanitarian crises, and cause long-term environmental damage across national boundaries.^[13] South Korea, Japan, and China would face immense pressure to coordinate emergency responses in a situation where preparation is minimal and institutional frameworks for cooperation are limited.

The international community would confront difficult decisions about intervention in North Korean territory to contain the disaster, all while navigating the unpredictable reactions of a regime that prioritizes survival above all else. Furthermore, North Korea’s potentially weakened state following such a disaster could invite external military intervention or internal political collapse, further destabilizing the region at a moment of acute vulnerability. Without U.S. leadership and capabilities to coordinate response efforts, regional powers might take unilateral actions based on narrow national interests rather than collaborative solutions.

Unexpected Disruptions in U.S.-Japan Relations and Resulting Strains in the Security Alliance

While the United States and Japan share a strong and longstanding alliance under the U.S.-Japan Security Treaty, any significant strain or perceived uncertainty in their relationship could disrupt regional stability. Reduced U.S. commitments could prompt Japan to reconsider its defense posture, potentially increasing military spending, accelerating modernization efforts, and forging stronger regional alliances.^[14] Although Japan’s pacifist constitution limits its military actions, a perceived lack of support from the United States may fuel debates on acquiring offensive capabilities. This shift could heighten tensions, particularly with China and North Korea, and risk accelerating a regional arms race.

Moreover, uncertainty around U.S. defense commitments might embolden regional actors to assert their territorial claims more aggressively. Without firm U.S. backing, disputes in areas like the Senkaku/Diaoyu Islands could see increased confrontations. The Republic of Korea (ROK, South Korea) may also recalibrate its defense strategy in response, further complicating regional security dynamics. Domestically, concerns over national security could strengthen nationalist voices in Japan, pushing for constitutional reforms to expand military capabilities. To avoid such destabilizing scenarios, maintaining a transparent and robust U.S.-Japan alliance remains crucial for preserving regional peace and deterring aggression.

Taiwan Conflict Escalation

A U.S. disengagement from Asia would dramatically increase Taiwan’s vulnerability, potentially prompting China to intensify efforts to unify Taiwan by force.^[15] Without a credible U.S. deterrent, the cross-Strait military balance would tilt decisively in Beijing’s favor, raising the likelihood of miscalculation and military conflict. Chinese planners might calculate that a narrowing window of opportunity exists to resolve what they consider an internal matter before Taiwan develops more robust independent defense capabilities.

The Quad (U.S., Japan, India, Australia) would face significant challenges in formulating a cohesive response without U.S. leadership and military capabilities. Individual members would need to weigh their economic relationships with China against their security interests and democratic values, potentially leading to possible fractured responses that embolden rather than deter Chinese aggression. A Taiwan conflict would seriously disrupt global supply chains, particularly for semiconductors, creating worldwide economic repercussions.^[16]

Emergence of New Security Architectures

In the absence of reliable U.S. security commitments, regional players would likely form new multilateral security arrangements designed to fill the power vacuum. Japan, Australia, and India could deepen defense ties through expanded joint exercises, intelligence sharing, and coordinated diplomatic positions. These nations share democratic values and concerns about China’s growing influence, providing a foundation for meaningful cooperation. Similarly, South Korea might forge stronger connections with European powers like France and the United Kingdom, both of which have expressed renewed interest in Indo-Pacific security.

These emerging security architectures would likely be more fluid and less institutionalized than U.S.-led alliances, creating a more complex and potentially less stable regional order. Nations might pursue overlapping and sometimes contradictory security arrangements, hedging their bets in an uncertain environment. The absence of a clear regional hegemon could lead to competition between different security frameworks, complicating efforts to effectively address transnational challenges.

Climate-driven Crises and Natural Disasters

The Indo-Pacific region faces disproportionate risk from climate change and natural disasters, including severe typhoons, flooding, tsunamis, and earthquakes.^[17] These events could overwhelm regional response capacities, particularly in the absence of U.S.-led humanitarian assistance and disaster relief operations, which have historically been a cornerstone of American soft power in the region.^[18]

The suspension of United States Agency for International Development (USAID) funding would exacerbate these challenges, limiting the resources available for early warning systems, emergency response infrastructure, and recovery efforts.^[19] Local governments, often lacking the financial and logistical capacity to manage large-scale disasters, would face greater hardship. Additionally, reduction in USAID-supported capacity-building programs would impede the development of resilient disaster management systems.

Countries would need to establish independent disaster response mechanisms or rely more heavily on international organizations with limited operational capabilities. Regional initiatives such as the Association of Southeast Asian Nations’ (ASEAN) Coordinating Centre for Humanitarian Assistance on Disaster Management (AHA Centre) could play a larger role, but without USAID’s support, their effectiveness may be constrained. The vacuum left by diminished U.S. involvement might also prompt increased influence from other major powers, altering regional geopolitical dynamics. Ultimately, communities most vulnerable to climate impacts would bear the brunt of the consequences, facing longer recovery periods and heightened humanitarian suffering. The absence of USAID’s assistance would hinder sustainable development efforts, undermining resilience against future disasters in the Indo-Pacific region.

China, with its expanding naval reach and growing humanitarian assistance capabilities, could position itself as a regional first responder, enhancing its influence at a moment of vulnerability for affected nations.^[20] Climate-driven migration and resource competition could further exacerbate existing tensions between states, potentially leading to confrontations related to fishing rights, water resources, and habitable territories. These challenges would test the resilience of regional cooperation mechanisms at precisely the moment when U.S. stabilizing influence is diminished.

Economic and Technological Implications

A reduced U.S. security presence in Asia would inevitably impact economic and technological landscapes throughout the region. The Indo-Pacific’s deeply interconnected supply chains and critical infrastructure rely on regional stability and freedom of navigation through vital waterways such as the South China Sea, the Strait of Malacca, and the Taiwan Strait.^[21] Uncertainty regarding security commitments could deter foreign investments, disrupt established trade routes, and hinder technological cooperation that requires trust between partners.

Furthermore, China’s Belt and Road Initiative (BRI) would likely gain greater traction in this environment, providing Beijing with expanded economic leverage throughout the region.^[22] Nations facing diminished U.S. support may seek Chinese investments and infrastructure development despite concerns about debt dependency and loss of sovereignty. The economic gravity of China, combined with its geographic proximity and growing technological capabilities, would exert a powerful pull on regional economies seeking stability and growth opportunities.

The technological landscape would similarly face potential fragmentation, with countries increasingly forced to choose between U.S. and Chinese digital infrastructure standards, telecommunications networks, and technology ecosystems.^[23]This bifurcation would be particularly challenging for smaller nations that lack the resources to develop indigenous alternatives and rely on international partners for technological advancement. The resulting “splinternets” could undermine regional connectivity and create new vulnerabilities in cybersecurity and critical infrastructure protection.^[24]

Regional Responses and Strategic Autonomy

Faced with the prospect of U.S. disengagement, Asian countries would likely pursue greater strategic autonomy through a variety of mechanisms. Japan, South Korea, and Australia would almost certainly accelerate defense spending and indigenous military technology development to reduce dependency on U.S. security guarantees.^[25] This would include investments in advanced missile systems, cyber capabilities, and intelligence gathering assets that provide independent deterrence options.

India, with its longstanding emphasis on strategic autonomy and non-alignment, could emerge as a key stabilizing force in this new environment. As the world’s most populous country with a growing economy and military capabilities, India might expand its naval presence across the Indo-Pacific and deepen security partnerships with like-minded democracies. However, India’s complex relationship with China and its traditional reluctance to form binding military alliances would create limitations on its role as a security provider.

Southeast Asian nations, particularly those with competing claims in the South China Sea, would navigate an increasingly delicate balance between Chinese influence and regional cooperation. ASEAN’s centrality in regional diplomacy could become increasingly vital, offering a platform for dispute resolution and confidence-building measures independent of great power competition. However, ASEAN’s consensus-based decision-making and the diversity of its members’ relationships with China would continue to constrain its effectiveness in addressing security challenges decisively.^[26]

Multinational Institutions and International Law

The erosion of U.S. security commitments would place additional pressure on multinational institutions and international legal frameworks to manage regional tensions. Organizations such as the United Nations, the ASEAN Regional Forum, and the East Asia Summit would need to evolve to address security challenges more effectively without U.S. leadership. International law, particularly the UN Convention on the Law of the Sea (UNCLOS), would remain an important framework for resolving maritime disputes, but its effectiveness would depend on collective enforcement mechanisms that might be weakened in a fractured security environment.

Regional powers might also establish new institutional frameworks designed specifically to address security concerns in a post-American context. These could include expanded roles for existing economic forums like the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) to incorporate security dimensions, or entirely new arrangements focused on specific challenges such as nuclear non-proliferation, maritime security, or cyber defense. The effectiveness of these institutions would depend on their ability to balance inclusivity with the capacity for decisive action—a perennial challenge in multilateral diplomacy.

Navigating an Uncertain Future

The potential withdrawal of the U.S. from its Asian security commitments would represent a seismic shift in the Indo-Pacific strategic landscape. While alliances may fray and adversaries may become emboldened, the region’s resilience will depend on the adaptability of its nations and institutions. By strengthening regional partnerships, investing in defense capabilities, enhancing multilateral diplomacy, and developing contingency plans for various scenarios, Asia can mitigate the destabilizing effects of U.S. disengagement.

The Indo-Pacific’s future will be shaped by its ability to navigate uncertainty and develop indigenous solutions to security challenges. As the United States recalibrates its foreign policy priorities, regional leaders must prepare for unexpected developments while working to preserve the regional stability that has underpinned decades of prosperity. This will require strategic patience, diplomatic creativity, and a willingness to transcend historical animosities in the interest of collective security.

Ultimately, even in a scenario of reduced U.S. presence, the nations of the Indo-Pacific retain considerable agency in determining their security environment. By embracing cooperation, resilience, and strategic foresight, they can maintain stability and prosperity in an era of geopolitical unpredictability. The choices made by regional powers in response to potential U.S. disengagement will shape not only Asia’s future but also the emerging global order of the 21^st century. Some of the changes and realignment may have permanence beyond Trump years at the White House.

^[1] Central Asia and US foreign policy under Trump – Hindustan Times

^[2] The United States’ Enduring Commitment to the Indo-Pacific Region | The White House

^[3] The INDOPAC Region: A Strategic Imperative For U.S. Security

^[4] China’s growing assertiveness in the South China Sea

^[5] China in the Taiwan Strait: February 2025 | Council on Foreign Relations

^[6] Democratic People’s Republic of Korea Continues Nuclear Weapons Programme, Violating Resolutions, Assistant Secretary-General Warns Security Council | Meetings Coverage and Press Releases

^[7] Indo-Pacific Strategy Update – Indo-Pacific Defense FORUM

^[8] Donald Trump and the Future of Multilateralism • The Global

^[9] The Latest: Trump questions value of NATO, slams Germany | AP News

^[10] Full article: Looking ahead: imbalance, dependency and NATO’s uncertain future

^[11] Total War: This Is What Happens If North Korea Fired A Nuclear Weapon In Anger – The National Interest

^[12] Total War: This Is What Happens If North Korea Fired A Nuclear Weapon In Anger – The National Interest