A South Korea-U.S. joint military exercise takes place in Yeoncheon, Gyeonggi Province, March 13, 2023. Yonhap

U.S. President Donald Trump appears to be tapping into European allies' security concerns about their geographic proximity to a conflict zone to prod them into doing more for their defense — a move keenly watched in South Korea, a U.S. ally that confronts persistent threats from an adjacent North Korea.

Trump has repeatedly said that the continental United States is an "ocean" apart from Russia's war in Ukraine as he doubled down on his call for North Atlantic Treaty Organization (NATO) member states to make greater security contributions.

The president's threat perception has raised a consequential question for South Korea: what if he writes off North Korea's advancing nuclear and missile threats as a faraway challenge in a way that could cast doubts over America's security commitment to South Korea.

As he did during his reelection campaign, Trump took aim at European allies this week, saying the protracted war in Ukraine is "far more important to Europe than it is to us."

"We have a big, beautiful ocean as separation," he wrote on Truth Social.

The remark came as Trump has called for NATO member states to spend 5 percent of their gross domestic product (GDP) — much higher than the 2 percent guideline that NATO leaders committed to in 2014.

Separated by the Pacific and Atlantic Oceans, the continental U.S. has been regarded as relatively safer than its Asian and European allies though the diffusion of military technologies and the development of long-distance weapons systems have reduced the advantage of the geographical separation from potential adversaries.

But Trump's explicit mention of the U.S. being an ocean apart came amid lingering concerns about potential gaps in the threat perception between the U.S. and its allies, like South Korea, which relies on America's nuclear umbrella to counter unabated threats from a recalcitrant Pyongyang.

"The threat perception of the U.S. — a country insulated by two oceans — cannot help but be notably lower compared with other allies," Kim Tae-hyung, the president of the Korean Association of International Studies and political science professor at Seoul's Soongsil University, said.

"That said, relatively weaker countries in the (U.S.-led) alliance architecture, including European countries, South Korea and Japan, cannot help but be worried about potential abandonment by the (stronger) ally. Trump appears to be relishing this situation and looking to maximize the benefit from it in future transactions with allies," he added.

During an interview with Yonhap News Agency in May last year, Elbridge Colby, Trump's nominee for under secretary of defense for policy, touched on the notion of an "asymmetry of perspective" between Seoul and Washington in reference to the allies' threat perceptions.

"The fundamental fact is that North Korea is not a primary threat to the U.S. It would not be rational to lose multiple American cities to just deal with North Korea. That's a different calculation for South Korea," he said. "We need to realistically evaluate an approach."

Geographic proximity is one of the four criteria used to evaluate threats from another state, according to an international relations theory proposed by Stephen Walt, a renowned professor at the Harvard Kennedy School. The other criteria are the country's aggregate strength or power, its offensive capabilities and its offensive or hostile intentions.

Though the allies are geographically far apart, it has been a top security priority for South Korea to remain on the same page with Washington in terms of the analysis of North Korean threats and policy tools to address them, particularly at a time when Pyongyang has been forging ahead with its nuclear and missile programs amid a deepening military alignment with Moscow.

U.S. President Donald Trump speaks in the Oval Office at the White House in Washington, D.C., Feb. 21. EPA-Yonhap

Walt said that Trump is "correct" that the war in Ukraine is of greater immediate importance to Europe than to the U.S. But he pointed out that the situation in Asia is different "because China is a potential hegemon in Asia, and the U.S. does not want it to dominate the entire region."

"For this reason, I do not think Trump wants to allow North Korea to attack a U.S. ally — including South Korea — as this would make him look weak and undermine stability throughout the region," the professor told Yonhap News Agency via email. "But I could be wrong, as Trump is already doing some things that have surprised me."

Some interpreted Trump's "ocean" remark along the lines of his seemingly selective isolationist tendencies, which were seen in his decision to withdraw the U.S. from the Paris climate agreement, the World Health Organization and the U.N. Human Rights Council.

Such tendencies under his America First credo have given rise to a flurry of speculation over whether Trump would consider reducing or even pulling out the 28,500-strong U.S. Forces Korea (USFK), and whether he would again demand a hefty rise in Seoul's share of the cost for stationing USFK.

Aaron Friedberg, political science professor at Princeton University and security aide to Vice President Dick Cheney from 2003-2005, brushed aside concerns about the likelihood of Trump moving to renounce America's security commitments to its allies.

"President Trump has often expressed his view that our European allies need to do more to strengthen their defense. At a minimum, these latest comments should encourage them to do this, and more quickly than many may have planned," Friedberg told Yonhap News Agency via email.

"I do not think that Trump's comments necessarily signal an imminent withdrawal of U.S. forces from Europe or the complete abrogation of our security commitments to our allies there. There is no evidence of strong public support in this country for such a move."

The professor went on to say that although Trump's comments have stirred much critical commentary from some Republicans as well as Democrats with a major debate over related issues shaping up, it is by no means obvious what the outcome will be.

"We don't yet know how the president will approach similar issues with our Asian allies. No doubt he will continue to press for greater defense contributions from Korea, Japan and others," he said. "But, at least to judge from the comments of some of his advisors, the administration intends to focus more attention and resources on Asia to counter the rise of Chinese power."

Friedberg raised the possibility that Trump might try to reach some deal with China on trade and other issues, which he said "could conceivably lead to a lessening of U.S. security commitments in Asia as well as Europe." He did not elaborate on the "other issues," but appeared to be referring to geopolitical issues, namely the South China Sea and the Taiwan Strait.

"The opposition to such moves, from Congress and portions of the public, would be even stronger than what we have seen thus far regarding Europe," he said. "It would be premature to conclude that the U.S. will turn its back on its longstanding friends and allies and retreat into a 21st century form of isolationism."

Eric Heginbotham, the principal research scientist at the MIT Center for International Studies, cast Trump's recent statements on Ukraine as "a large number of bad ideas for America hiding behind one good idea."

"The good idea is that Europeans should do more for their own defense. But the bad ideas in his recent statements are many: the decision to treat with Putin; using Putin's own language to define the responsibility for the war in Ukraine; and excluding Ukraine and Europe from negotiations," he told Yonhap News Agency via email.

"Trump's statements have gone beyond fair burden sharing and imply he will seek concessions to Russian aggression in Europe."

Heginbotham added that concessions to Russia, if made, could encourage Chinese aggression.

"All of this may sound appealing to some in the United States who no longer wish to bear the burden of defense, but it will also harm American interests, not just those of our allies and partners, many of which have in the past shown us deference in the economic domain," he said.

Many agree that after dealing with more pressing global issues, such as the war in Ukraine and the conflict between Israel and the Hamas militant group, Trump might put more focus on Indo-Pacific matters, likely including the "burden sharing" issue with South Korea.

Bruce Bennett, a senior defense analyst at the RAND Corp., said that Trump could call for Seoul to spend 3 percent of its GDP on defense.

"Years ago, the ROK committed to raise its percentage of GDP spent on defense to 3 percent, but this percentage has in practice stalled at around 2.5 percent, and the size of the active-duty ROK military has now fallen from 690,000 to around 500,000 personnel, in part due to demographics and in part due to political decisions to reduce the time draftees serve in the military. And all of this during a time when the North Korean threat has been growing," Bennett said.

ROK is short for South Korea's official name, the Republic of Korea.

"It should therefore not be surprising that President Trump would ask the ROK to increase its defense spending. But I do not believe that we have seen such a request yet. When we do, a ROK defense budget of 3 percent of GDP would be a likely request from Trump, since the ROK previously committed to such," he added.

Last year, Robert O'Brien, who served as national security advisor for Trump from 2019-2021, stressed the need for South Korea to increase its defense spending to 3 percent or 3.5 percent of its GDP. (Yonhap)