What year did the United States enter World War II?
The United States entered World War II on December 7, 1941 after the attack on Pearl Harbor by the Japanese.
Complete the following task based on the instruction and optional input provided.### Instruction:
What year did the United States enter World War II?

### Output:
The United States entered World War II on December 7, 1941 after the attack on Pearl Harbor by the Japanese.