When did the US enter World War 2?
December 8, 1941 was the date of the US declaration of war, but
in fact the US was at war on December 7, 1941 at about 7:55 AM when
the Japanese attacked Pearl Harbor, Hawaii.
This war, while not unexpected, was not the war the US wanted to be
in because it was felt that Germany was the greater threat. Hitler
didn't declare war against the US until December 11, 1941, in
support of his Axis agreements with Japan.
The USA entered World War Two a day after the Japanese attacked
the US navy base of Pearl Harbor in Hawaii on December 7, 1941.
After declaring war on Japan, Germany declared war on the USA.
Thus, the US entered a two front war.