David Flin
Gone Fishin'
Even in OTL with defender advantage, Entente had problems like the French mutinying. Not to mention that I have got the impression that morale in general was drown the drain by 1918, with the American reinforcements seeing Entente troops as some sleepwalkers - please correct me if I'm wrong.
The French mutinies weren't strictly a mutiny in the sense of "We don't want to fight this war anymore." They were more akin to: "We don't want to fight this war in this bloody silly way, and sort out the sodding organisation. Rations are rubbish, rotation is falling apart, and we aren't that keen on large-scale frontal assaults."
The troops weren't demanding an end to the war, they were demanding that it be fought more competently. They were happy enough to defend their lines, and even undertake small-scale offensives with clearly defined objectives that had a reasonable chance of success. The rotation system had fallen apart through lack of staff interest in making it work, and some troops were spending too long in the front lines while others got forgotten in the R&R areas. Rations were not getting through properly because of pilfering along the route.
To describe it as the French being on the verge of pulling out is to misunderstand what the mutinies were about. When Nivelle was sacked and Petain took his place, Petain promptly ended mass offensives, and switched to limited attacks with massed artillery. He also sorted out the rotation system. Problem over.
Amazingly, the German never even noticed there was an issue. German intelligence during the War was not exactly awe-inspiring.
As for the American reinforcements - it depends on the American. The Black American units that were put under French command (because Pershing didn't want them in the American Army) thought highly of the poillu. They also learned from the experience of those who had been fighting, as opposed to the rest of the American forces who had to learn the same old lessons all over again because they thought they knew better than the Europeans.