American isolationism refers to the foreign policy approach where the United States avoids involvement in international conflicts and alliances. This stance was particularly prominent in the years following World War I, as many Americans believed that staying out of European affairs would prevent future wars and protect national interests. During the Great Depression, isolationist sentiments grew stronger, leading to policies that restricted immigration and limited trade with other nations. However, this approach shifted dramatically with the onset of World War II, as the U.S. recognized the need to engage globally to combat threats like Nazi Germany and Imperial Japan.