Just days before Trump’s first UN speech [transcript], the Congressional Research Service produced U.S. Role in the World: Background and Issues for Congress (Sept. 15, 2017 R44891). From the introduction:
The overall U.S. role in the world since the end of World War II in 1945 (i.e., over the past 70 years) is generally described as one of global leadership and significant engagement in international affairs. A key aim of that role has been to promote and defend the open international order that the United States, with the support of its allies, created in the years after World War II. In addition to promoting and defending the open international order, the overall U.S. role is generally described as having been one of promoting freedom, democracy, and human rights, while criticizing and resisting authoritarianism where possible, and opposing the emergence of regional hegemons in Eurasia or a spheres-of-influence world.
Certain statements and actions from the Trump Administration have led to uncertainty about the Administration’s intentions regarding the future U.S. role in the world. Based on those statements and actions, some observers have speculated that the Trump Administration may want to change the U.S. role in one or more ways. A change in the overall U.S. role could have profound implications for U.S. foreign policy, national security, and international economic policy, for Congress as an institution, and for many federal policies and programs.