Answer :
Final answer:
The U.S. entered World War II in 1941 after Japan's attack on Pearl Harbor, approximately 2 years after the start of WWII in Europe.
Explanation:
The U.S. entered World War II on December 7, 1941, after Japan's attack on Pearl Harbor, marking the catalyst for American involvement in the conflict. The time period between the start of WWII in Europe and the U.S. entering the conflict spans from the outbreak of WWII in 1939 with the German invasion of Poland to the U.S. declaration of war in 1941, totaling approximately 2 years.
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