Trump and Southeast Asia: When Transactionalism Undermines Trust

Just over a year into US President Donald Trump’s second term, his administration’s strategy in Southeast Asia is finally starting to crystallise. Washington’s increasingly transactional inclinations in areas such as the South China Sea and critical minerals threaten to erode its bank of trust that has made America the preferred regional power in the past.

Rather than focusing on values promotion or on explicitly countering China, Trump has clearly prioritised acquiring critical minerals and maintaining the security of supply chains in support of semiconductor manufacturing and AI. Because the US is now more self-interested and transactional than ever, at times Washington will feel comfortable engaging with authoritarian regimes that it once shunned, potentially resulting in a significant rewiring of its traditional alignments across the region.

A central priority for the Trump administration is the safeguarding of commercial shipping lanes. Trump’s recently-released National Security Strategy (NSS), for instance, argues that a Chinese attack on Taiwan would gravely harm US interests not only because the island “provides direct access to the Second Island Chain”, but because one-third of global shipping transits the South China Sea annually. Notably, the document downplays geopolitical and humanitarian consequences in favour of an explicitly economic rationale. Trump’s new National Defense Strategy from earlier this month likewise emphasises the need to maintain a region in which “trade flows openly and fairly” — to the exclusion of all else.

This blunt framing is unsettling for ASEAN states trying to resist China’s expansive sovereignty claims in the South China Sea. While sustained US attention to the region is broadly welcomed, motivations matter. Washington’s presence is driven primarily by economic self-interest. As such economic calculations shift — whether through deeper decoupling from or renewed engagement with China — Washington’s approach towards the region will change accordingly.

The Philippines offers a revealing test case. To be sure, Philippine President Ferdinand Marcos Jr. held a productive White House meeting with Trump in July. Additionally, the US–Philippines alliance has in fact been strengthened at both the operational and institutional levels. This includes the establishment of Task Force Philippines, a unit focused on planning and intelligence sharing in contested waters; the FY2026 National Defense Authorisation Act (NDAA) authorising up to USD2.5 billion in military assistance for the Philippines for 2026-2030 and the reinstatement in 2025 of USD500 million in military aid initially approved under the Biden administration. Washington has also agreed to increase the tempo of bilateral exercises, including the most recent joint US–Philippines patrol near Scarborough Shoal in 2026.

But under an America First approach, one could argue that defending Manila’s exclusive economic zone from Chinese incursions is not inherently a US responsibility. Taken to its logical extreme, this logic raises doubts about whether Washington would back the Philippines in a conflict over features like Second Thomas Shoal or Scarborough Shoal. It remains unclear how highly the Mutual Defense Treaty ranks among Trump’s priorities, particularly when weighed against economic considerations and his interest in a potential grand bargain with Beijing.

… in trying to shed the costs of responsible leadership, the US may ultimately forfeit its most valuable strategic asset in Southeast Asia, which is the trust that once made US power not only dominant, but preferable across much of the region.

Vietnam faces comparable anxieties, but without the benefit of a formal US security treaty. Hanoi elevated relations with Washington to a “comprehensive strategic” status in 2023 to deepen alignment, including in the South China Sea. Yet Trump’s narrowly defined priorities suggest Washington may hesitate to support Vietnam’s maritime claims absent a clear payoff for the US.

Beyond maritime security, the administration has intensified efforts to secure critical minerals. In October, the US signed mineral agreements with Cambodia, Malaysia, and Thailand, while pressing Indonesia for access to its nickel, cobalt, manganese, and copper — key inputs for US supply chains and efforts to counter China.

More controversially, Washington has explored access to Myanmar’s rare earths despite the country’s civil war, reportedly considering engagement with both the junta and rebel groups in exchange for sanctions relief. While progress has been limited, the episode illustrates the increasingly transactional nature of US regional policy.

Supply chains linked to AI are another focus. Last month’s “Pax Silica” initiative aimed to secure inputs for advanced semiconductor production, but named only Singapore as a Southeast Asian partner, alongside several US allies and partners, and with Taiwan as a guest. This raises further questions about which regional states Washington views as strategically essential.

One nation that may be ripe for the Trump administration’s entreaties is Laos. With its estimated critical mineral deposits and the ease with which Trump negotiates and seemingly befriends autocrats, Vientiane may feel compelled to ink new agreements with the US, especially if it means lower reciprocal tariffs (currently at 40 per cent) and other perks. Whether or not such outreach materialises, the fact that Laos is even conceivable as a partner underscores how dramatically US priorities in Southeast Asia have narrowed.

Although prior US administrations also prioritised access, routes, and resources, they did so with greater emphasis on alliances and values. The Trump administration has broken from that tradition, signaling that engagement depends on demonstrable benefit to the US. As the NSS bluntly puts it, “The days of the United States propping up the entire world order like Atlas are over.”

Southeast Asian governments are hard-nosed and transactional, not sentimental. If US engagement is reduced to a ledger — for example, shipping lanes secured here, minerals accessed there — regional states who are typically friendly with Washington will respond accordingly. They could broaden their partnerships, resulting in weakening US leverage, as well as hedging more decisively toward China. The long-term effect would not be greater American influence, but diminished standing — a region less willing to align with Washington, less confident in US staying power, and less prepared to take risks on America’s behalf.

However, there will also inevitably be some authoritarian nations which historically have been less friendly with the US, like Cambodia, Laos, and Myanmar. They will welcome and benefit from an America that is now acting more like China: values-free and focused like a laser on economic interests in its partners.

But overall, in trying to shed the costs of responsible leadership, the US may ultimately forfeit its most valuable strategic asset in Southeast Asia, which is the trust that once made US power not only dominant, but preferable across much of the region. Ultimately, China will be the beneficiary.

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