（从左至右）澳大利亚副总理理查德·马尔斯、日本外务大臣岩屋毅、北约秘书长马克·吕特、新西兰总理克里斯托弗·拉克森、韩国国家安全顾问魏圣洛在2025年6月25日举行的海牙北约峰会上

二战后，美国在亚太广大地区保持着几无争议的主导地位。在“旧金山体系”或“轴辐”架构下，美国建立了军事同盟，提供经济援助，并积极介入该地区事务。美国政策的战略基础有赖双边和多边防务协议，如与日本（1951年）、韩国（1953年）、菲律宾（1951年）、澳大利亚和新西兰（统称ANZUS，1951年）以及泰国（1954年）的协议。

美国向该地区提供经济援助，并在重建中发挥了作用。它通过“道奇计划”支持日本稳定经济，并在朝鲜战争（1950-1953年）后向韩国提供援助。美国主导的IMF和世界银行也向各国提供了援助。同时，华盛顿向欧洲盟友施压，要求它们放弃在亚洲的殖民地。美国的经济和技术援助推动了1960-1990年代“亚洲四小龙”（韩国、香港、新加坡和台湾）的崛起。

美国目前正扭转这些政策。这一逆转趋势早就出现，但唐纳德·特朗普总统2025年1月开始的第二任期内的政策加速了这一进程。他的“美国优先”政策正在重塑美国与亚太国家在国防、联盟模式和经济领域的关系。

特朗普将美国对亚太盟友的承诺与“更高的成本、更多的要求和不一致的条件”挂钩。他敦促盟国将国防预算提高到GDP的5%，并在共同安全领域承担最大份额。针对印度购买俄罗斯武器和石油，特朗普加征关税，这是近年来两国关系首次遭受重大打击。他的政策引发该地区许多国家民众的不满和外交紧张局势。例如，日本取消了原定于7月1日与美国举行的“2+2”会谈；澳大利亚总理安东尼·阿尔巴尼斯公开拒绝美国大幅增加国防开支的呼吁；日、澳、韩高层领导人缺席海牙北约峰会，只派出级别较低的官员；韩国国防部正式拒绝了增加国防预算的要求。

除了导致双边关系紧张，特朗普的政策还影响到至少两个美国主导的小多边安全框架：日美印澳四方安全对话（Quad）和澳英美安全伙伴关系（AUKUS）。2007年成立的Quad旨在协调印太地区的人道主义援助和救灾行动，加强海上安全。2017年重启后的Quad则是为了深化在海上安全、关键基础设施、互联互通、供应链韧性和新兴技术方面的战略合作，以推动“自由、开放和基于规则的印太地区”，暗中反对中国的政策。然而，由于美国疏远了与其他成员的关系，该机制未来的有效性目前尚不确定。

同样，AUKUS也面临不确定的未来。AUKUS于2021年启动，旨在为澳大利亚配备先进的核动力潜艇，并在网络、人工智能、量子技术和海底作战等前沿领域建立三边合作框架，其战略意图是对抗中国在印太地区日益增长的军事影响力。

五角大楼正在审查与澳大利亚和英国共享核动力潜艇技术的AUKUS协议。

2024年3月10日，洛杉矶级快速攻击潜艇“安纳波利斯”号停靠在西澳大利亚罗金厄姆西舰队基地的迪亚曼蒂纳码头。（MC2 Kaitlyn Eads / 美国海军）。

2025年6月，美国国防部启动对价值3680亿澳元（约2400亿美元）的AUKUS协议的正式审查，评估其是否符合特朗普政府的“美国优先”议程和美国国防工业利益。该审查由负责政策的国防部副部长埃尔布里奇·科尔比牵头，预计将在未来几个月内完成。英国和澳大利亚都公开强调对AUKUS的承诺，但也承认在美国政策不确定情况下对该项目的未来感到担忧。美国与日本、澳大利亚和印度等主要战略盟友的关系脱节，引发了人们对Quad和AUKUS未来前景的忧虑。

在经济领域，与二战后美国的经济援助和市场开放政策不同，特朗普政府实行了保护主义。从4月2日即所谓“解放日”开始，他加征了一系列高额关税。尽管美国已经与一些国家签下贸易协定，并正与其他国家进行谈判，但所有亚太国家都深受这些关税的影响。即使在最终达成的贸易协定里，美国的关税也明显高于4月2日之前的水平，例如相较“解放日”之前，美国对日本的关税达到15%，对韩国关税为15%，对越南关税为20%。

加征关税前，特朗普政府大幅还削减了美国的全球对外援助，包括削减美国国际开发署资金、全球卫生项目、给世界粮食计划署的捐款、气变项目及公共广播。2025年6月，特朗普政府向国会提交了一份报告，提议削减关键领域83亿美元的对外援助。虽然特朗普政府的这种做法有其自身理由，但关税和援助削减严重影响了特别脆弱的经济体和小国。例如，太平洋小岛国首当其冲地受到了援助削减和高额关税的双重打击。

特朗普政府迅速、单方面地实施这些重大变革，并未与地区国家进行协商，导致许多国家陷入恐慌。大多数国家选择不回应，担心受到美国的进一步报复，但它们的不满情绪显而易见。

亚太地区的二战后安全框架在结构上已经过时，与该地区的快速变化格格不入，特朗普政府的政策更加速了它的瓦解和分裂。日本、韩国、澳大利亚和印度等盟友对美国政策表达了担忧，Quad和AUKUS的命运正标志着这种瓦解。许多地区国家认为，如果它们必须承担自身国防费用并支付高额关税才能进入美国市场，那么采取符合本国议程的政策要比遵从美国的路线更好。

不断演变的模式表明，由于美国承诺的不确定性，该地区主要国家将增加国防预算，同时重新评估与其他国家尤其同中国的关系，虽然过去它们寻求美国的支持与之抗衡。如今，与中国进行不受美国安全承诺影响的接触将为它们提供新的思考角度。其实，这种趋势始于特朗普第二任期之前，2024年日本、韩国、澳大利亚和印度等国的对华关系已经升温。

此外，这些国家中等强国地位的日益增强，也促使它们建立自身能动性和民族主义观，而不是被当作美国亚太战略的次要参与者。例如，日本有自己的愿景，并希望利用它来塑造地区政治。同样，印度长期以来一直保持战略自主，并偏爱小多边主义。一旦亚太地区由外部强加的安全秩序减弱，就可能导致地缘经济取代地缘政治，小多边主义和多极化取代单边主义。

许多分析人士认为，特朗普应对美国在亚太地区影响力的变化（下降）负责。但深入分析表明，特朗普只是结果，而非原因。美国是“大国兴衰”这一人类历史常见主题的典型案例。美国全球霸权的过度扩张、盲目支持以色列在加沙被占地带实行种族灭绝的道德破产、不断攀升的债务以及日益恶化的经济问题，都意味着美国政策应有结构性转变。特朗普正试图用自己的方式解决美国这些积弊。美国在亚太地区数十年的影响力正在发生变化，谁将填补这一空白，该地区未来的安全格局将如何演变，仍有待观察。

From left: Richard Marles (Deputy Prime Minister, Australia), Takeshi Iwaya (Minister of Foreign Affairs, Japan), NATO Secretary General Mark Rutte, Christopher Luxon (Prime Minister, New Zealand), Wi Sung Lac (National Security Advisor, Republic of Korea) meet at the NATO summit in The Hague, Netherlands, June 25, 2025. (Photo: NATO)

In the post-World War II period, the U.S. maintained nearly uncontested supremacy over the vast Asia-Pacific region. Under the San Francisco System, or the 'Hub and Spokes' architecture, the U.S. established military alliances, provided economic assistance, and proactively engaged with the region. The strategic foundation of U.S. policy relied on both bilateral and multilateral defense agreements, such as those with Japan (1951), South Korea (1953), the Philippines (1951), Australia, New Zealand (collectively known as ANZUS, 1951), and Thailand (1954).

The U.S. provided economic assistance and played a role in the region's reconstruction. It supported Japan through the Dodge Plan to stabilize its economy and, following the Korean War (1950-1953), offered aid to Seoul. The U.S.-led IMF and the World Bank also assisted various countries. Washington pressured its European allies to relinquish their colonies in Asia. U.S. economic and technological assistance contributed to the rise of the Asian Tigers, South Korea, Hong Kong, Singapore, and Taiwan, from the 1960s to the 1990s.

The U.S. is now reversing these policies. While this reversal trend had started earlier, the policies of President Donald Trump during his second term, beginning in January 2025, accelerated it. His 'America First' policy is reshaping U.S. relations with Asia-Pacific countries in defense, alliance patterns, and economic domains.

Trump is linking the U.S. commitment to Asia-Pacific allies with 'higher costs, more demands, and inconsistent conditions.' He pushed allies to increase their defense budgets to 5 percent of GDP and bear the lion's share in common security. Trump imposed heavier tariffs on India for purchasing Russian arms and oil, marking the first significant blow to U.S.-India relations in recent times. His policies sparked public dissatisfaction and diplomatic tensions in many countries of the region. For instance, Japan cancelled its planned 2+2 meeting with the U.S. set for July 1; Australia's Prime Minister Anthony Albanese publicly rejected U.S. calls for a significant boost in defense spending; top leaders of Japan, Australia, and South Korea skipped the NATO summit in The Hague and instead sent lower ranking officials; South Korea's defense ministry formally rejected the demand for an increase in defense budget.

Besides straining bilateral relations, Trump's policies have affected at least two U.S.-led minilateral security frameworks: the Quad (Quadrilateral Security Dialogue), which includes Japan, the U.S., India, and Australia, and AUKUS (Australia-United Kingdom-United States). The Quad was established in 2007 to coordinate humanitarian assistance, disaster relief, and strengthen maritime security in the Indo-Pacific region. After its revival in 2017, the Quad aimed to deepen strategic cooperation on maritime security, critical infrastructure, connectivity, supply-chain resilience, and emerging technology to promote a 'free, open, and rules-based Indo-Pacific,' implicitly opposing China's policies. However, by alienating all other members, the future effectiveness of the mechanism is now uncertain.

Similarly, AUKUS faces an uncertain future. Launched in 2021, AUKUS was designed to equip Australia with advanced nuclear-powered submarines and to establish a trilateral framework for collaboration in cutting-edge areas such as cyber, artificial intelligence, quantum technologies, and undersea warfare, with the strategic intent to counter China's growing military influence in the Indo-Pacific region.

The Pentagon is reviewing the AUKUS agreement on sharing nuclear-powered submarine technology with Australia and the United Kingdom.

The Los Angeles-class fast-attack submarine Annapolis pulls alongside Diamantina Pier at Fleet Base West in Rockingham, Western Australia, on March 10, 2024. (MC2 Kaitlyn Eads / U.S. Navy)

In June 2025, the U.S. Department of Defense initiated a formal review of the A$368 billion (approximately US$240 billion) AUKUS deal, assessing whether it aligns with the Trump administration's 'America First' agenda and U.S. defense industrial interests. The review, led by Under Secretary of Defense for Policy Elbridge Colby, is expected to be completed in the next few months. Both the UK and Australia have publicly emphasized their commitment to AUKUS but acknowledge concerns about the project's future amid U.S. policy uncertainty. The disconnect in U.S. relations with key strategic allies Japan, Australia, and India raises doubts about the future of both the Quad and AUKUS.

In the economic sector, unlike the post-WWII U.S. policy of economic assistance and opening markets, the Trump administration adopted protectionism and imposed a series of steep tariffs starting from April 2, the so-called 'Liberation Day.' Although the U.S. has signed trade deals with some countries and is negotiating with others, all Asia-Pacific countries have been deeply affected by these tariffs. Even in the final trade agreements, U.S. tariffs are significantly higher than those that existed before April 2. For instance, the tariffs with Japan are set at 15%, with South Korea at 15%, and with Vietnam at 20%, compared to what existed before 'Liberation Day.'

Prior to the tariffs, the Trump administration significantly reduced U.S. global foreign aid, including cuts to USAID funding, global health programs, contributions to the World Food Program, climate change, and public broadcasting. In June 2025, the Trump administration submitted a report to Congress that proposed cutting US$8.3 billion in foreign aid in key areas. While the Trump administration's approach has its own rationale, these tariffs and aid cuts have severely impacted especially vulnerable economies and small countries. For instance, small Pacific Island Countries faced the brunt of simultaneous aid reductions and heavy tariffs.

The Trump administration implemented these significant changes quickly, unilaterally and without consulting regional countries. This caused a state of panic for many nations. Although most countries chose not to respond, fearing further retaliation, their discontent was evident.

The post-WWII security architecture in the Asia-Pacific had become structurally obsolete, mismatched with the rapid changes in the region; policies of the Trump administration accelerated its erosion and fragmentation. Expressing concerns against U.S. policies by allies such as Japan, South Korea, Australia, and India, the fate of the Quad and AUKUS signals this erosion. Many regional countries believe that if they have to bear the burden of their own defense and pay steep tariffs to access the U.S. market, it would be better to adopt policies that align with their own national agendas rather than toeing the U.S. line.

The evolving pattern indicates that major regional countries will increase their defense budgets due to uncertainties surrounding U.S. commitments. At the same time, they will reassess their relations with others, particularly with China, against whom they had sought U.S. backing. Engaging with China independently of U.S. security commitments would provide them with a new perspective. This trend had already begun even before Trump's second term. Japan, South Korea, Australia, and India, among others, had started to warm up to China by 2024.

Furthermore, the growing middle power status of these countries compels them to develop their own agency and nationalistic outlook rather than being seen as secondary players in the U.S. Asia-Pacific strategy. For example, Japan has its own vision that it aims to use to shape regional politics. Similarly, India has long maintained strategic autonomy and a preference for minilateralism. Once an externally imposed security order in the Asia-Pacific weakens, it could lead to geoeconomics superseding geopolitics, and minilateralism and multipolarity superseding unilateralism.

Many analysts hold Trump responsible for the shifts (read decline) in U.S. influence in the Asia-Pacific. A deeper examination shows that Trump is an effect, not the cause. The U.S. represents a typical case of the 'rise and fall of great powers,' a common theme in human history. The overstretched global hegemony of the U.S., exposure of its moral bankruptcy as seen through its blind support for Israeli genocide in occupied Gaza, the mounting debt, and compounding economic challenges necessitated structural changes in U.S. policies. Trump is trying to address these accumulated American problems in his own way. The decades-old U.S. influence in the Asia-Pacific is changing. Who will fill the void and what the future security structure of the region will be, remains to be seen.