I think Quebec would be more analogous to Louisiana or New Mexico. Language alone won't prevent statehood. Quebec would be bilingual with its own cultural identity at first, but Quebecois language/culture would probably decline under American rule due to standardized English education and cultural assimilation, and Quebec would be primarily Anglophone by today..
unlike new mexico and lousianna, french-canadians would have represented the majority of the population within their state unless it was forcefully split with chunks added to other states which, unless well planned, would result in *more* bilingual states.
The problem from my point of view extended beyond simple language. Assuming the annexation was done with the local population's approval, you have to remember that french-canadians had constitutional guaranteed to their own clerical controlled education and legal system (and post 1867 the veto or 1980, the notwithstanding clause) which, one would assume, they would want to retain. Since it's doubtful that US policy makers would accept to have a state with different protections or to have said protection extended to others, a "separate yet equal" sort of arrangement would seem like a safer bet.