when did the us enter ww2

The United States officially entered World War II on December 8, 1941, the day after Japan's surprise attack on Pearl Harbor on December 7, 1941. Following President Franklin D. Roosevelt's "Day of Infamy" speech, Congress declared war on Japan. Subsequently, on December 11, 1941, Nazi Germany and Italy declared war on the United States, which then entered the European Theater of the war as well.