The America First Committee was founded in September 1940, during a time of significant isolationist sentiment in the United States as the nation grappled with the implications of World War II. One notable event that demonstrates this isolationist feeling occurred earlier that year, specifically in May 1940, when Germany's rapid advance through Western Europe prompted widespread concern about the possibility of American involvement in the conflict.
The fall of France to Nazi Germany and the subsequent evacuation of British forces from Dunkirk were pivotal moments that heightened isolationist sentiments. Many Americans believed that the United States should avoid becoming entangled in Europe's conflicts, as evidenced by public opinion polls and rallies that expressed strong opposition to entering the war. This backdrop of isolationism contributed to the formation and support of the America First Committee, which actively campaigned against intervention and sought to keep the U.S. out of the war.