It's a simple concept, really, one which makes sense if you think about it as an average Canadien/ne would have seen it. (And I
do mean Canadien/ne - the usage of "Québec" to designate something other than the town whose area the original Mi'kmaq word describes originated with the British, and did not sink in; note too that even the Continental Congress, in one of its few gestures north of the border, consistently calls the territory "Canada" and referring specifically to that area, not to the modern concept that includes what would be called at that time "British North America". Also, before ~1840 or so, anyone who lived in Canada, was descended from the original founding peoples (with exceptions for the Irish), and natively spoke French was considered a Canadien; everyone else was either American or British.) From the time span between 1755/1763 and 1775 the Canadiens were already drifting away from France and looking to live in peace with the new overlord - but that difference already manifested itself prior to the Conquest - as I've already mentioned a few times before, so I'm sounding like I'm repeating myself.
First off, the Québec Act - or, to give it its formal name, the British North America (Quebec) Act, 1774 (14 Geo. III c. 83). No, it was not given act as a random act of kindness, nor for that matter was it to pacify the French-Canadians. Also, it wasn't a sui generis solution just specifically for Canada. That kind of legislation was actually built on precedent deep into British history, of which Scotland was one example (as a union of equals) and before that with what we now call the Crown dependencies (the Channel Islands and the Isle of Man). Even Wales and Ireland temporarily fell into this before their forced integration into England (in the case of Wales) or the UK (in the case of Ireland - and even then Ireland still retained a civil service based at Dublin Castle and its own body of law and legal system). The case of Canada initially fell into the Welsh/Irish mold of things, as the product of a conquest. So the Québec Act was nothing new nor ground-breaking. Now, having noted that I don't think that Britain would be as generous for the rest of the Empire - the Southern Cone included - as it did for Canada, because of the peculiar local dimension of the Québec Act, one which gets overlooked in discussion of this piece of legislation. Of all the colonies within the British and French empires, Canada and Acadia were actually unique and was set out as a different example from France itself. What should be kept in mind when talking about New France and the Conquest is that rather than as a bog-standard colonial enterprise which France applied to its Caribbean colonies and the rest of the Global South, New France was specifically founded as a reaction against the Wars of Religion tearing apart Europe, France included.
Its founders, including such luminaires like Champlain (who's a quite enigmatic figure himself) and Louis Hébert (one of New France's early governors), conceived New France as one where Catholic and Protestant could coëxist quite peacefully with each other, as if the Wars of Religion never happened, and as part of the Nouveau Monde as a place where Aboriginal people could quite happily be both themselves and as positive and co-equal contributors of New France society. In that sense it was an idealized version of France itself which was better than the France of reality, one which was rooted in the desires of ordinary people. To pilfer some pre-1960s traditional French-Canadian nationalist language (though for a completely different purpose), from the beginning of its conception New France was considered special, as the product of a messianic mission to be an example to the mère-patrie of how things should be like rather than how it became. Now there were those at Versailles (Cardinal Richelieu among them) who tried to subvert that ideal and tried to make New France fit into a box, but fortunately that didn't really happen at all - indeed, we have documentary evidence existing in archives in both France and Canada where successive members of the colonial bureaucracy constantly complained to the Palace about those "ingrates" who threw out all convention and protocol as the bureaucrats and élites themselves knew it and basically had ideas well above their rank and station. In effect the habitants were engaging in a quiet rebellion with the mother country which made life difficult for Versailles - so when the Treaty of Paris came around the French were glad to get rid of their vast holdings in North America - it just simply wasn't worth it, between a perceived disobedient population and a financial sinkhole sunk deeply into a fur industry which did not provide the type of quick riches found in France's Caribbean colonies.
And as for the Conquest? The Canadiens just simply carried on as they always did and well honed with their experiences with French colonial bureaucracy basically applied the same tactics to the British conquerors. They weren't going to let something as pesky as a religious test (which officially barred Catholics from openly practicing their religion and participating in public life) to stand as a barrier. The difference? The British Army was willing to go along, as far as it could, until they received orders from Whitehall to act differently. In reality things kept going on as before because the Army quickly realized that if they actually carried out its instructions the place would fall apart rather quickly. All the Québec Act did was just provided a de jure stamp of approval to what had been going on de facto and which required an insane amount of figleaves to cover it all up, thanks to the persistence of the Canadiens in insisting in carrying on life as it always had; the British basically very quickly learned the lesson the French did not when it opened Pandora's box. But any colonial power could have done the same bargain in Canada the British did, and for proof of that we actually have Louisiana. When Louisiana became part of the Spanish Empire in 1763, the Spanish administered Louisiana much like how the British Army initially administered Canada. Indeed, so much of Louisiana life continued as it did under French rule that the administrators in Havana required translators who could explain in Spanish what was going on. Now, granted, much like with the British in Canada, the Spaniards did try to make Louisiana a proper Spanish colony but just like with Canada, that didn't really work out as planned. Had Louisiana remained Spanish after 1802 (instead of being retroceded to France) and thus became part of Mexico one New Spain became independent (for la Luisiana was formally a district of the Viceroyalty of New Spain) I would not be surprised if the arrangement continued and thus Louisiana would remained as before, only with the administration based in Mexico City rather than Havana. Would certainly make for an interesting TL.
Which brings up an essential difference between Spanish America and New France. While New France was formed in reaction to events in Europe, Spanish America was founded as an extension of Spain in the New World, as an expansion of the Reconquista. The institutions set up by the Spanish and which were inherited by its successor nations reflected this fact as well as its tendency to leave well enough alone (particularly in cases like Mexico and Peru) and just expanded on what already existed. [...] While French-Canadians loved to complain about Anglo-American capital and the British/Anglo-Canadian colonizers conspiring to keep French-Canadians down and in their place, French-Canadians honestly didn't have anything comparable to the rest of the Global South despite the poverty of the majority since even in the dark ages of French-Canadian history there was always some retention of the fluidity of French-Canadian society and an unusually remarkable ability to adapt to new situations; French-Canadians never lived in a society as rigid as that which existed in the British Empire in the Global South.
As it turned out, there were many cases in Canada where the British occupiers, with the tacit consent of those who were colonized (and a keen sense of bending the law and looking the other way to make things work, in an early case of "
para Inglés ver" (
explained on the Portuguese Wikipedia) long before that concept arrived in Latin America), allowed things to go on de facto within their new colony that they would never have allowed either back home or within its already existing colonies. For example, many bureaucrats, civil law notaries, and other officials who did not join the boats crossing the Atlantic back to Europe were basically expected to work as per normal, even with the restrictions due to the Oath of Allegiance, even up to the point IIRC of using English "substitutes" (if that term could be used here) as cover for the real bureaucrats. Heck, even
the Vicar-General and later Bishop of Quebec at the time was "drafted" in to help, since Catholicism was never really banned and Canadiens who wanted to remain religious and those British who wanted a docile populace knew how to jump the hoops within British law to permit the free exercise of Catholicism despite the letter of the law mandating the establishment of the Church of England in the then-Province of Quebec. In effect, during all this time no serious effort was made to introduce Protestantism in Canada - at least not until the British lost during the American Revolution. Or, if you want to put it another more racist and stereotypical way, the British were so overcome and seduced by a certain sense of Latin charm and sensibility introduced to them by the French in Canada that the colonizer ended up with no other choice
but to fight to preserve the rights of their newly colonized, whether or not they wanted to do so. In that sense, therefore, the Canadiens were never subject to the same restrictions as what the Irish experienced, and even without the
Quebec Act the situation would likely be the same in Canada as IOTL before the
Quebec Act came into being and thus everyone would bend over backwards to make sure everything was working as it should, the law be damned and whether or not the Catholic Church was given legal recognition. All the
Quebec Act did was to legitimize the situation so that the British Army in Quebec didn't have to feel embarrassed when explaining their conduct unbecoming to their superiors; it basically didn't change a thing on the ground except giving peace of mind to both Westminster and Whitehall - the first Canadian victory on the road to gradual independence, if you will. Of course, the rest of what was the early version of British North America did not see things that way, seeing as the
Quebec Act was lumped in with all the other "Intolerable Acts".
The British recognized early on, even w/o Guy Carleton, that if they tried Anglicizing the population from the word go it wasn't going to work as the entire place would stop functioning. So the British engaged in a lot of deception with their overlords to ensure that both sides were satisfied, even with the Oath of Allegiance taken into account. As I see it, Canada with no Quebec Act would be no less different that with the Quebec Act in place IOTL; the only differences would be related to the British already on the ground trying to make sure their cover didn't get blown because then things would get wicked problematic very fast. Then and only then would you get a largely indifferent and very pragmatic and accommodating populace joining the rebels against the advice of almost everyone, the Catholic Church and the nationalist élites be damned. (Their cousins across the Atlantic would probably be horrified, of course, even when supporting the US elsewhere and otherwise, but at that point there was nothing they could probably do - it was already out of their hands to begin with, even during the French colonial period.)
For one thing, at this point in time (until IOTL the Rebellions in the late 1830s) whatever nationalism existed among Canadiens was much different from the traditional French-Canadian nationalism we're all accustomed to. Much like the vast majority of the populace, Canadien nationalism tended more towards the pragmatic side of things. This was the crux of their general attitude towards anyone in power as well as their indifferent to neutral attitude towards the Americans. Respect them for who they are and they'll reciprocate by trying to stay in your good graces (with beneficial results for both sides). If you try pushing them towards uncomfortable positions (as IOTL the Château Clique found out to its detriment), then expect a similar reaction in turn (even if it means linking up with those who want to lash out against the UK for their own reasons). For the period, well before the Americans caught on, that was a liberal position to take, which makes sense for a people whose nationalism at this point in time was pretty liberal and tolerant to begin with and which frustrated Versailles a lot as well as the British during the 1820s and 1830s.
How does that context apply here, in a TL;DR fashion? Very simple. The last time France ran the place, they totally misunderstood what was really happening in their largest colony because they tried to make it fit into a "familiar" mold, which totally failed because the Canadiens were all too well aware of the newfound opportunities that presented itself being on the other side of the Atlantic. (Hence the legends surrounding
les coureurs des bois et les voyageurs, who actually existed in real life, as well as complaints within the colonial bureaucracy that the Canadiens are all too eager to "go native" instead of acting like proper
paysans, like their Third Estate counterparts back in the metropole.) Not only that, but New France in general was fast becoming a financial sinkhole which was never financially viable to begin with. So, when France saw an opportunity to dump New France they took it. Essentially, the habitants 'welcomed' the arrival of the British and the British responded in kind by bending over backwards (even violating British law at the time - until, thanks to the wonders of Parliamentary supremacy, they managed to pass a law legitimizing the status quo) to make the new colony feel welcome. The
Quebec Act, as it were, was the crowning achievement of this early phase; while the general scholarly and historical analysis tends to focus more on the reaction of the remaining post-Conquest élites of Canadien society at the time, it also had a positive effect on ordinary people as well, essentially an affirmation that
oui, one can be both neutral/loyal to the British while maintaining Canadien identity and Canadien society at the same time, that both were equally complementary.
As for the French, however - there's a reason why for a long time in French-Canadian society they were almost always referred to as "les maudits Français" (the damned French) - not only did they 'abandon' the place (though the sense of abandonment was actually a later construct of nationalist historians), but they never really "got" the place. Canadien society in general was glad to see the backsides of the French and their colonial administration, who were focused on other things instead of actually governing the country. Now, whether the Palace and the associated bureaucracy saw it that way or not would be a different story, but as far as Canadiens were considered the Palace didn't register into their consciousness. The metropole was a different country to them. So the departure of the French from the scene was essentially not on the best of terms - and both sides knew this. In that sense, the Continental Congress' Letters to the Inhabitants of Canada were wrong, completely - if they wanted to make their message more effective, to many Canadiens the "arbitrary, tyrannical government" they would have had in mind immediately was the French,
not the British. That the US ended up having France as one of its main foreign allies, from a Canadien POV, was therefore most unfortunate because as far as they were concerned it showed that if the rebels (oops, Patriots) wanted to make the trek North again, they would have simply lost the plot and that the Canadiens themselves were absolutely in the right to stay neutral at first and then eventually kick the Americans out of their country. Never mind what the priests said at Sunday Mass; never mind what the British had said that to support the rebels was to engage in treason (and had the force to back it up) - in the end, it was an effort of Canadiens and Canadiennes to extirpate the Americans.
Which brings me back to the American Revolution and the Quebec campaign. Let's assume, for the sake of argument (since having an American presence in Canada is absolutely key to making the OP work), that the Continental Congress decides to approach the Canadiens differently from OTL. Now, having the Letters to the Inhabitants of Canada translated into French was a good first step - they probably knew that if there was support for independence from Britain, it would come from the Anglophone minority, so to bring the Francophone majority on board they would need to address them in their native language. The trouble with the French translations, however, was that they really did not
translate them right - often times in the scholarly analyses of the Letters you tend to notice that among Francophones themselves the trouble was they were baffled and confused by the whole thing, and that was because trying to bring the political context of the Continental Congress' grievances against London up north was highly inappropriate for the Canadien situation. The Canadiens in general did not have a clue what the Continental Congress was saying, and thus in general they tended to ignore them. (Of course, it also helped that the British confiscated every copy of the Letters they could find in circulation.) So for TTL purposes, let's assume that, thanks to their spies, the Continental Congress wises up and use a different approach with their French translations by situating them within the context of what your average illiterate Canadien (who has it read to them by someone who knows how to read and write) would already find familiar - in other words, blame the French, acknowledge that the British are trying the best they can to win the hearts and minds of Canadiens, but that
we who want to create a new country have a better option and that it would be in Canada's best interest to join
us. (Even if it means muzzling the anti-French and anti-Catholic people in the Continental Congress' midst.) So they basically do what Canada would consider the right things - even to the point of having the Americans admit that maybe the British were onto something with the
Quebec Act and that it was not as "intolerable" as they led themselves to believe. (What the Americans
would find intolerable, though, was
how totally disorganized French civil law was at the time, because as customary law which was built upon by statutory law there was really no sense of urgency of codification on the part of the colonial administration.)
This leads expectations in Canada of their future status within the US towards one of two paths - on one hand, there's the pathway of joining the United States directly as a state (possibly with some compromises either in the Constitution itself, in the Enabling Act authorizing Canada's ratification of the Constitution, or both) or as an independent country with strong associational links with the US (say, for example, Canada retaining the Articles of Confederation as its basic understanding of the relationship between the two) if including a large amount of Catholics (and not just any sort of Catholics, but Catholics that were associated with the old enemy of English/British colonial times pre-1763) was that objectionable to the Founding Fathers. This would not, however, include having the old colonial master come back (and I think even the Palace knew this) - that would have been the last thing they would have wanted, since as far as the Canadiens were concerned they were finished with France, and vice versa. Therefore, any sense of France regaining Canada - if only just even the core of it, which IOTL under the British became Lower Canada (> Canada East > Québec) - would have to be something that would have to be in secret and kept as far away from the Canadiens as possible. There's good reason for this. If news came back to Québec (and then upriver to all the other settlements) that the French want to regain control over this area, the immediate reaction would have been an "oh, shit, not again" and/or a "what, in the name of God and the Most Holy Trinity, did we do to deserve this?" type of reaction. They knew already what it was like under the French and would much rather prefer not to revert to that type of situation again. On top of that, there's also the Britain factor. France would have interpreted that collaboration with the British was widespread - even among people who considered themselves neutral to the whole thing - and that because of the Canadiens' collective action post-Conquest they would need to be taught a "lesson", which the French would interpret as bringing "the Caribbean treatment" to Canada by treating it as a bog-standard colonial enterprise - with some reprisals, of course, for perceived disloyalty (whether true or not) through collaboration with the enemy. Unfortunately for the French, the Canadiens would have already known what that "lesson" would entail - they've already been aware of what happened to their fellow Acadian brethren, who frustrated both Britain and France alike with their staunch neutrality (leading to their ethnic cleansing/near-genocide in the heat of war at the instigation of New Englanders who coveted the Acadians' land) - and therefore the Canadiens would be determined not to let something like that happen again. In other words, by promising 'Quebec' to the French, the Continental Army would have taken one step too far towards making a serious - and insensitive - mistake. Not only that, but the Continental Army would have committed an act of betrayal of the Canadiens' trust - once again, the Canadiens have been abandoned to their fate; once again, another overlord failed to "get" the Canadiens and their society. This time, though, there's now an additional feeling that they've been used in order to deliver them back to
les maudits Français - and they don't like that.
So, what would the Canadiens do in such a situation? Having been pushed too far into an uncomfortable position, they would prefer to rebel and get out from being under the French - passively, at first, and then gradually more active once they get the self-confidence to simply declare independence. Once active warfare happens, it's only a matter of time before the French decide to pack up shop and leave. All the more so because Louis XVI was basically indecisive and weak, which only tended to exacerbate situations and make them worse rather than better (and in the case of the American Revolution, the exacerbation here was the draining of the French Treasury); if he had to flee France for [the Town of] Quebec (which is basically a last-minute desperate situation), he'd only do it if he was forced out by circumstance. He is no João VI, that's for sure; Louis XVI is not going to receive the same treatment João VI received when he fled to Rio. Eventually, the whole monarchy/colonial business gets thrown of Canada (not to mention sliding out of the control of the US), as the Canadiens decide the best arbiters of their fate, present situation, and future development is themselves. And that is that.