What event precipitated the U.S. entry into World War II?

The attack on Pearl Harbor is the pivotal event that precipitated the U.S. entry into World War II. On December 7, 1941, the Japanese Imperial Navy launched a surprise military strike against the United States naval base at Pearl Harbor in Hawaii. This attack resulted in significant loss of life and damage to the Pacific Fleet, with over 2,400 Americans killed and numerous ships and aircraft destroyed.

In the immediate aftermath of the attack, there was a surge of patriotic fervor and public support for entering the war among the American populace. The following day, President Franklin D. Roosevelt delivered a famous speech referring to December 7th as "a date which will live in infamy," and he requested a declaration of war against Japan from Congress, which was overwhelmingly approved.

The other events mentioned, such as the invasion of France, the sinking of the Lusitania, and the Battle of Britain, were significant in their own right but did not directly lead to America’s involvement in World War II. The invasion of France occurred in mid-1940, a time when the U.S. was still largely isolationist. The sinking of the Lusitania took place in 1915 during World War I, and while it stirred American sentiments