The document discusses how World War II transformed the United States into a global superpower. It summarizes President Roosevelt's 1941 "fireside chat" where he told Americans that the country would win the war and the ensuing peace. As a result of its newfound power at home and abroad, American culture was reshaped for the rest of the 20th century. The war cost 50-70 million lives worldwide and introduced the possibility of nuclear warfare, radically changing global politics for decades to come. The post-war period saw the emergence of the Cold War between the U.S. and U.S.S.R. as they built up nuclear arsenals and allied smaller nations to their sides.