During the Cold War, U.S. leaders often spoke of the United States as the leader of the Free World, its role to protect nations from Communist oppression and make the world safe for democracy and freedom. This perception of America’s role had deep roots. When the United States declared its independence from England in 1776 and established a new form of government—which expanded the scope of individual freedom—Americans saw themselves as champions of a new world. Foreign policy scholar Itai Sneh explains how this vision has long shaped American policies: “Their self-perception as role models for the rest of humanity behooved Americans to conduct a foreign policy that espoused tolerance and self-reliance and that accorded protection to the weak from the abuse of power through observance of the fundamental...