Since World War I, US policy has been split between isolationism and internationalism. From debates over joining the League of Nations to intervention in Europe, Americans have found odd comfort in siding with one of these two camps.
The isolationists wanted to avoid being mired in foreign intrigues, wars, and crises. The internationalists argued that without involvement, the world would evolve in ways that lacked US influence and thus threatened its national security. On December 7, 1941, the internationalists won the debate.