What pivotal event led the united states to enter world war ii?

The bombing of Pearl Harbor by the Japanese military was the pivotal event that led the US to enter World War II.

On December 7, 1941, the US naval base in Hawaii was attacked by the Japanese. This attack resulted in the deaths of over 2,000 American citizens and military personnel. The day after this attack, President Franklin D. Roosevelt gave his famous address to Congress, asking them to declare war on Japan. The US officially entered World War II on December 8, 1941.

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cultural/diplomatic relations. most medieval japanese   culture has chinese origins. writing, architecture etc.