With his shocking victory in the US presidential election, Donald Trump has made history -- and made a lot of people very afraid. In fact, his rise threatens to incite a revolution that shakes the foundations not only of American politics, but also of global peace and prosperity. One region that is likely to start feeling tremors soon is Southeast Asia.

Throughout his campaign, Trump espoused an “America first” worldview, emphasizing that he would follow through on US international commitments only when it suits him. This has rattled many a US ally and partner, including the countries of Southeast Asia, which fear that they will be all but ignored by a key guarantor of stability in their neighborhood.

This would represent a notable reversal from the last eight years, during which President Barack Obama made a concerted effort to deepen America’s ties with Southeast Asia. Under Obama’s stewardship, the US acceded to the Treaty of Amity and Cooperation in Southeast Asia, and joined the East Asia Summit.

Moreover, in 2013, the US became the first ASEAN dialogue partner to establish a permanent mission to the organization. Last year, the country forged a strategic partnership with ASEAN. And, earlier this year, Obama hosted the first US-ASEAN summit on American soil. Obama also brought four ASEAN members into the Trans-Pacific Partnership, a mega regional trade deal that would promote US economic exchange with the region.

Obama also helped to cement bilateral ties with most countries in the region, visiting nine out of 10 during his two terms in office. If a US government shutdown had not forced him to cancel a trip to Brunei in 2013, he would have had a perfect record.

To be sure, America’s ties with Thailand and the Philippines have deteriorated somewhat during Obama’s second term, owing to the US president’s criticism of violations of democratic norms and human rights in both countries. But that regression has been more than offset by progress in America’s relationships with Indonesia, Laos, Myanmar, Singapore, and especially Vietnam.

Obama’s efforts in Southeast Asia were all part of his broader strategic “pivot” to Asia, announced in 2011. Aimed at helping the US to maintain its strategic primacy in the Asia-Pacific region, the policy has been quietly welcomed by most regional actors, as it dovetails with their desire to check China’s hegemonic ambitions in the region.

All of this may be about to change. Trump is likely to focus overwhelmingly on domestic issues, at the expense of America’s strategic interests abroad. Indeed, he may well back away from strategic engagement with ASEAN and its members, causing their relationships with the US to deteriorate. If he fails to show up at important regional meetings like the East Asian Summits, that deterioration will become even more pronounced.

Trump’s indifferent attitude will also hurt bilateral relations. To be sure, Malaysia, Thailand and the Philippines may prefer a US president who does not trouble himself to criticize their governments’ human-rights abuses, corruption, or constitutional shenanigans. But US relations with other countries in the region may stall, if not deteriorate, as confidence in Trump’s willingness to follow through on US commitments collapses.

Economic ties are also likely to suffer. Under Trump, who has revealed strong protectionist tendencies, the TPP will stay moribund, at best. The US-ASEAN Connect initiative, which Obama proposed at the summit earlier this year, and which aims to boost America’s economic engagement with the regional grouping, may also go nowhere.

It is not only Southeast Asia that will suffer from Trump’s indifference. Australia, India, and Japan -- key US allies and security partners in the Asia-Pacific region -- may also find it difficult to connect with Trump, further undermining faith in the US-led regional security architecture. The strategic rebalancing toward Asia that Obama worked so hard to advance may be thrown into reverse, dealing a heavy blow to Asia and the US alike.

One Asian country that may welcome the election’s outcome: China. Though Trump has criticized China extensively for supposedly stealing American jobs -- and even blamed it for creating the “hoax” of climate change -- he may take a softer stance on Chinese strategic expansionism in the region, especially in the South China Sea, than Obama did.

In a far-fetched but not implausible scenario, Trump may even strike a deal with China over its territorial claims, disregarding the interests of US allies, from Japan to the Philippines. Such a move would be particularly devastating to perceptions of Trump’s America in Southeast Asia.

The good news is that this outcome is not guaranteed. Campaign rhetoric is one thing; governing is quite another. Once in the White House, a heavily advised Trump may realize that maintaining some continuity in America’s foreign policy, particularly in the Asia-Pacific, is more in line with US interests than the alternative. If nothing else, Trump may resist the idea of China gaining strategic primacy in the region.

For Trump, who made his career in real estate, perhaps the best way to look at it is in business terms. The US would be remiss to squander all the significant investment that his predecessor has made in Southeast Asia.

By Le Hong Hiep

Le Hong Hiep is a fellow at the Institute of Southeast Asian Studies-Yusof Ishak Institute in Singapore. -- Ed.

(Project Syndicate)