What impact did American entry have on the world war 1?

When the U.S. entered the war on April 6th 1917, both the Central and Allied powers were hoping the U.S. would join them because the U.S. troops were fresh and they weren't tired like Germany or France. When the Germans started to invade France and push the French back, they came upon a barrier of U.S. troops at the Argonne forest who forced Germans to retreat. simply stating, the U.S. was a lot more confident in victory and they weren't tired unlike any other country that was fighting in the war.