French mutiny did not mean refusal to defend

Without American reinforcements, could France still hold the Western Front against Germany?

Probably. The French mutinies rejected further attacks rather than defence, while the blockade and weak German logistics continued to limit how far an offensive could go.

The shorthand that the 1917 French Army had simply refused to fight is misleading. The mutinies were largely a refusal to make more costly advances, not a refusal to defend French positions. Germany still faced the economic pressure of blockade and an army whose supply system could not sustain unlimited movement into France. American troops helped consume German reserves and supplies more quickly, but their arrival was not the only barrier to a decisive breakthrough. In this counterfactual, imperial troops released after an American peace could later reinforce the Western Front, though their redeployment would take time. The likely result is a harder and differently timed campaign rather than automatic French collapse.