Question

What impact did the U.S. joining the Triple Entente have on the war?

Answer 1

The answer is the third option 

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~Jordan~

Answer 2

American forces ended the stalemate on the western front leading to Germany's defeat

The large amounts of fresh US troops, equipments, and other needed war material quickly overwhelmed the already about to give up German soldiers, who were low on supplies and tired from the war.

hope this helps