Final answer:
The attack on Pearl Harbor led to the US entering World War II, due to its aim to prevent US intervention in Japan's Asian expansion.
Step-by-step explanation:
The attack on Pearl Harbor in 1941 by Japan indeed prompted the United States to enter World War II. The attack was a calculated risk by Japan to prevent U.S. interference in their expansion throughout Asia, leveraging the opportunity presented by European conflicts. Following the attack, the United States transitioned swiftly from peacetime to being an arsenal of democracy, gearing up its economy for wartime production and rallying public support for the war effort against Japan and the Axis powers.