When did the U.S. join World War II?

1 Answer
May 1, 2018

After the attack in Pearl Harbor on Dec, 7th 1941

Explanation:

The USA joined WWII after the Japanese attack on Pearl Harbor on Dec 7th 1941, it was a military base in Hawaii.

The USA did not declare war only on Japan but on its allies that is to say Germany and Italy( the Axis).