His challenges were limited in the first term.

Stephen Chaudoin, Helen V. Milner, and Dustin Tingley, “‘America First’ Meets Liberal Internationalism,” in Chaos Reconsidered: The Liberal Order and the Future of International Politics, Eds. Robert Jervis, Diane N. Labrosse, Stacie E. Goddard, and Joshua Rovner, Columbia University Press 2023, pp. 370-371.

A central claim we made before the start of Trump’s term1 was that his attempts to change American foreign policy would be constrained by domestic and international forces. In terms of domestic constraints, elements of American democracy— its checks and balances— would make radical change difficult. As we will show, agents within key institutions did in fact push back against many of the Trump administration’s policy changes. The usual suspects, like Congress, interest groups, and the American foreign policy and military bureaucracies, played large roles. The judicial system was a surprisingly strong and unexpected constraining force. The media also kept keen attention on the changes proposed by the administration. Trump would have been able to make many more changes had he faced fewer domestic constraints. As Robert Jervis argues in chapter 1, “some realities proved obdurate.”

The second set of constraints arose from international pressure on the United States, especially in the reactions to confrontational and unilateral policies that Trump pursued. Trump wanted to change relations with U.S. allies by making them do more for themselves and pay more; he also wanted to negotiate new deals with the country’s partners, competitors, and enemies. But the United States’ allies and enemies remain the same today as they were four years ago. Our interdependent planet favors engagement, cooperation, and multilateralism. Unilateral policies are unlikely to advance America’s main goals; indeed, they are likely to backfire and undermine its security and prosperity. A belligerent Russia and a rising China make American cooperation with its allies ever more important. And so multilateral engagement remains in America’s national interest as the best strategy for securing peace and prosperity.

Overall, Trump was unable to fundamentally change the direction of U.S. foreign policy. While the tone did change, the underlying policies were often constrained, as we expected. At the same time, Trump’s foreign policy weakened the United States. His undiplomatic rhetoric, his norm- breaking behavior, and his inconstant policy maneuvers alienated America’s allies and friends and instilled greater boldness in its competitors and enemies. All of this left the United States with a less secure position in world politics at a time when China’s rise creates new uncertainties.