Postwar superpower

The United States and Soviet Union jockeyed for power after World War II during a new Cold War, dominating the military affairs of Europe through the North Atlantic Treaty Organization (NATO) and the Warsaw Pact. The United States promoted liberal democracy and capitalism, while the Soviet Union promoted communism and a centrally planned economy, but both sides supported dictatorships when politically convenient and engaged in proxy wars, including the Greek Civil War and the Korean War. As the Communist Party in the Eastern Bloc suppressed dissent, American anti-communists like Joseph McCarthy attempted and failed to suppress their opposition at home.

Meanwhile, America experienced a period of sustained economic expansion. A growing civil rights movement headed by prominent African Americans such as Martin Luther King Jr. fought racism, leading to the abolition of the Jim Crow laws in the South and passage of the Civil Rights Act of 1964. Following Kennedy's assassination in 1963, his successors expanded a proxy war in Southeast Asia into the unsuccessful Vietnam War. As a result of the Watergate scandal, in 1974 Richard Nixon became the first U.S. president to resign, rather than be impeached on charges including obstruction of justice and abuse of power.

The election of Ronald Reagan as president in 1980 marked a significant rightward shift in American politics. In the late 1980s and 1990s, the Soviet Union's power diminished, leading to its collapse. The leadership role taken by the United States and its allies in the United Nations–sanctioned Gulf War and the Yugoslav wars helped to preserve its position as the world's last remaining superpower and to expand NATO.