Impact if the Americans had been involved in the Battle of Passchendaele

If the US had entered and mobilized for the war at an earlier date to be ready for Passchendale July-November 2017 what impact would that have had on the war?
 
Passchendale July-November 2017
Wait, the war is still going? :p

Anyway,
I assume such a scenario must involve an early PoD. Maybe the more belligerent Theodore Roosevelt wins the 1912 election?
If the US enters World War I a year earlier than IOTL, then the cornucopia of american stuff will be available for the Entente sooner, shortening the war. Germany would try to hasten the peace negotiations with Russia in order to free up troops to counter the americans coming from the west, but i doubt they would be able to, what with Kerensky still in control with Russia and with more reasons to keep in the war (mainly, the Entente doing better at Passchendaele).
 
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