The main effect of the Quebec act was the replacement of common (English) law with civil law. And of course the toleration of Catholics. Both were welcome by the habitants. And this was one of the grievances of the Americans:
"For abolishing the free System of English Laws in a neighbouring Province, establishing therein an Arbitrary government, and enlarging its Boundaries so as to render it at once an example and fit instrument for introducing the same absolute rule into these Colonies"
So the Americans were pretty unrealistic in expecting much help from the habitants. (Which didn't stop them of course