According to [the 1778 treaty](https://en.wikipedia.org/wiki/Treaty_of_Alliance_(1778) between the US and France, the French agreed to renounce any territorial claims they had to Canada or other parts of mainland North America. On the other hand, the Americans tried to convince the French to aid them in an invasion of Canada, with the promise that France would receive additional fishing rights in return.

But the French dragged their feet on this question, and secretly supported the policy of keeping Canada in British hands.

That being said, the Comte d'Estaing - the admiral of the French fleet - assumed in 1778 that an invasion of Canada was imminent, and drafted a letter addressed to Canadians (Déclaration adressée au nom du roi a tous les anciens François de l'Amerique septentrionale) promising them they would be protected by the French King if they surrendered.

Appealing to their ties to the mother country, D'Estaing promised the inhabitants of Quebec liberation in the case of invasion - although he conveniently did not specify if they would become part of the United States or France.

The declaration was distributed in Canada and in the Illinois country, and seems to have helped inspire a rebellion in Vincennes (in present-day Indiana). But the plans for an invasion were never realized, and Governor Haldimand quickly clamped down on dissent in Quebec.

There were a number of plans of invasion that were subsequently vetted between 1780 and 1783, but it's not clear that any of them had much support from the Canadian population.

Source: Marcel Trudel, Louis XVI, le congrès américain et le Canada, 1774-1789.