Lafeyette and some of the other nobles actually idealized our fight. Lafeyette wasn't just an idle noble, he was a member of the French Kings war council, even at his young age.
One might also note that the Declaration of Independence was written with the French in mind.
...Then the French went and used our same words and phrases, and totally misunderstood their meaning.
But it was not enough to convince me that the French would have become involved had we been fighting against anyone other than England.
Remember that in the late 1700's there were more than a few Huguenots in the colonies: and they're relationship wasn't all warm and fuzzy.
Actually, I think the difference was because the Americans were a "Moral and Religious People," (John Adams), who were already used to self-government.
The leaders of the French Revolution, OTOH, were neither moral nor religious, and the French people were not in any way ready for self-government.
Well, I wouldn't hold that against them too much. Our own politicians do the same thing. For a few decades they did so only infrequently, now they do it routinely.