Final answer:
The United States joined the Allied powers in WWI due to economic interests and German aggression.
Step-by-step explanation:
The United States joined the Allied powers and fought in World War I primarily for two reasons:
- Economic interests: The US had significant economic ties with the Allies, particularly Britain and France. Their victory was crucial to protecting US trade and investments.
- German aggression: Germany's unrestricted submarine warfare and the Zimmerman telegram, where Germany proposed an alliance with Mexico against the US, provoked the US to join the war to defend its national security.
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