Final answer:
The USA entered World War II in 1941 due to Japan's attack on Pearl Harbor.
Explanation:
The USA officially entered World War II in 1941 because of Japan's attack on Pearl Harbor on December 7, 1941. This event served as the catalyst for America's involvement in the war, leading to the nation joining the conflict.
Learn more about USA's entry into World War II here:
https://brainly.com/question/36931384
