Final answer:
The U.S. entered World War I in 1917 due to German actions and communications.
Step-by-step explanation:
The U.S. entered World War I in 1917. The main reason the U.S. entered the war was the German policy of unrestricted submarine warfare, which threatened American lives and commerce. Additionally, the interception and decoding of the Zimmermann Telegram, in which Germany proposed an alliance with Mexico against the U.S., played a significant role in the U.S. decision to enter the war.
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