The entry of the US into the entente did help the United Kingdom and France, it was in no way a decisive factor and did not turn the tide. By the time the US entered WW1, the Central Powers were already doomed to lose. Both the German Empire and the Austro-Hungarian Empire by 1917 were completely exhausted from the stalemate and the British blockade. The entente could easily import necessary goods from other nations and their massive colonies. The French and the British have massively improved their technology and were able to easily produce war materials and also began producing tanks. The Germans did not have any chances to break through the massive fortifications of the small frontline of the Entente without completely exhausting their army. By this time, Russia already made peace with Germany, so the US couldn't have helped them outside of the civil war. Germany would defiantly not applaud a new nation entering against it. And we can clearly see that the entrance of the US did not turn the tide for the Entente.
