Why did Germany’s acts of terrorism and attempt to influence Mexico ultimately backfire?

They ultimately just provoked the Americans into joining the war as their enemies.

Explanation:

Germany started by sinking American ships that were sending supplies to the British and French who the Germans were at war with. Civilian ships were caught in this crossfire as well (see: the Luisitania) which greatly increase tensions between the Americans and the Germans. This tension came to a head when the Germans sent the Zimmerman telegram to Mexico, asking them to attack the U.S. so that they would be distracted and wouldn't join the war in Europe. The British intercepted this telegram and showed it to the Americans, who then used it as justification for war against Germany.

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