Following World War II, the United States emerged as one of the two dominant superpowers, the Soviet Union being the other. The U.S. Senate on a bipartisan vote approved U.S. participation in the United Nations (UN), which marked a turn away from the traditional isolationism of the U.S. and toward increased international involvement.^{[86 ]}The primary American goal of 1945–1948 was to rescue Europe from the devastation of World War II and to contain the expansion of Communism, represented by the Soviet Union. U.S. foreign policy during the Cold War was built around the support of Western Europe and Japan along with the policy of containment, stopping the spread of communism. The U.S. joined the wars in Korea and Vietnam and toppled left-wing governments in the third world to try to stop its spread.^[87]

In 1989, the fall of the Iron Curtain after the Pan-European Picnic and a peaceful wave of revolutions (with the exception of Romania and Afghanistan) overthrew almost all communist governments of the Eastern Bloc. The Communist Party of the Soviet Union itself lost control in the Soviet Union and was banned following an abortive coup attempt in August 1991. This in turn led to the formal dissolution of the USSR in December 1991, the declaration of independence of its constituent republics and the collapse of communist governments across much of Africa and Asia. The United States was left as the world's sole superpower.