* The Russian Revolution (1917): The Russian Revolution led to the overthrow of the czarist regime and the establishment of the Soviet Union. The revolution had a major impact on American politics and society, as it inspired some Americans to embrace socialism and communism while others feared the spread of communism to the United States.
* The Great Depression (1929-1939): The Great Depression was a global economic crisis that began in the United States. The depression led to widespread unemployment and poverty in the United States, and it had a profound impact on American politics and society. The New Deal, a series of economic programs enacted by President Franklin D. Roosevelt, was designed to address the crisis.
* World War II (1941-1945): The United States entered World War II in 1941, after the attack on Pearl Harbor. The war had a major impact on the country, as it mobilized the entire nation and led to a boom in the economy. Over 400,000 Americans were killed in the war, and the country's role in defeating Nazi Germany and Japan made it a global superpower.
* The Cold War (1947-1991): The Cold War was a global conflict between the United States and the Soviet Union that lasted for over forty years. The Cold War had a profound impact on American politics, society, and culture, as it led to the development of a national security state, the rise of the military-industrial complex, and a heightened awareness of the threat of nuclear war.