The question is, what if the US did not join ww1. In France there were already uprisings and mutinities in 1917, which could hardly be subpressed. One main argument was, the US would enter the war. If that did not happen, I am sure until 1918 another rebellion would have brought France to surrender. But even if France can hold its position until 1918, there were more German soldiers available from the east at that date. Then, without US help, France was finally doomed.
Yes, Germany was also in a bad shape, but a collapse would not happen before 1919. As the Germans were only fighting on enemy soil in that time, in France, the morale was better than the French.
However I am sure if the US did not enter, France would have started peace negotiations in the 2nd half of 1917, at least at the beginning of 1918, when it was clear German soldiers would come from the east. When the danger of a too great defeat was too great.
Adler