My theory is no Quebec Act was needed to get the French to be loyal, it just formalised the official British policy up until then. However, for the Americans the Quebec Act was the straw that broke the camel's back. Many Virginians were land speculators and owned land west of the proclamation line in what according to the act was now Quebec. They were not too happy about the idea of seigneuries and tithes to the Catholic church spreading Ohio.
Early on the British were generally impressed with how loyal and peaceful the habitants of Quebec were. This is the impression I have from letters written at the time. The Quebec Act of 1774 simply rewarded the Quebecois formally for their loyalty. The seigneurial system had been recognised by the British in 1771 and they strengthened it rather than abandon it. This hampered American settlement in the area since most New Englanders scoffed at being under a seigneur (especially when over half of the seigneuries belonged to religious orders of the Catholic Church).
In late 1760 just after the conquest Abbot of Quebec, Monsignor Briand was paid 20 pounds by the English governor James Murray. So early on the British government knew how to use the Catholic Church to its advantage.
Below is part of Section IV of the 1763 Treaty of Paris, it shows how the British from the onset agreed to allow the French to continue to practise the Roman Catholic faith.
"His Britannick Majesty, on his side, agrees to grant the liberty of the Catholick religion to the inhabitants of Canada: he will, in consequence, give the most precise and most effectual orders, that his new Roman Catholic subjects may profess the worship of their religion according to the rites of the Romish church, as far as the laws of Great Britain permit. His Britannick Majesty farther agrees, that the French inhabitants, or others who had been subjects of the Most Christian King in Canada, may retire with all safety and freedom wherever they shall think proper, and may sell their estates, provided it be to the subjects of his Britannick Majesty, and bring away their effects as well as their persons, without being restrained in their emigration, under any pretence whatsoever, except that of debts or of criminal prosecutions: The term limited for this emigration shall be fixed to the space of eighteen months, to be computed from the day of the exchange of the ratification of the present treaty."
The British for the most part allowed a live and let live policy to operate in Quebec. The troubles began when the loyalists began arriving. They began pushing for a legislative assembly, which most Canadiens opposed (since in French history the only time an assembly was called was to raise taxes). As Anglos poured into Montreal and to a lesser extent Quebec City they began to dominate the commerce of the colony and began to accuse the French of disloyalty during the Napoleonic Wars. In reality most were simply apathetic to the British cause. The English speakers began demanding French assimilation in the Quebec Mercury (newspaper), the Parti Canadien was the response and they began printing Le Canadien. They're both fascinating to read since they polarised the two communities. However, the best of all is the Quebec Gazette beginning in 1764. Most of the front page stories tend to be month old news from France. The execution of King Louis XVI and later Marie Antoinette dominated for months on end. It's interesting because early on in the revolution (up until late 1792), the English press was supportive of the reforms taking place in France, while the Canadiens were disgusted by the treatment of the clergy. Once the king was imprisoned both sides seemed to have agreed. There were even revolutionary agitators that tried to stir up revolutionary sentiment in Quebec, but they had little success.
And on an ending note, there were Quebec French willing to help out the Americans, but as I said above when they started to pay in worthless paper money, people were not happy, and it shows from reading letters of people at the time to each other. Any good will the Americans had seemed to have evaporated the moment they ran out of silver.
