There was a mixed class composition to the American "revolution." There were significant renter and smallholder components. Good examples would be the Ethan Allen boys kidnapping the governor of New York or the Boston Rent riots.

The Mercantile and slave owning class was able to channel this energy with promises to seize Indian land and lower the price of goods. Add in nascent patriotism and you've got a revolutionary cocktail.

Also, not only the US participated in the war. The French ruling classes saw it as an opportunity to weaken England's imperial hold, and the Mohawk fought with their American allies against the English who were encroaching on their land from the north.

The Mercantile class were the main organizers, but calling petite bourgeois grievance the driving force is unfair.

Edit: there was also a sort of duel (or even quintuple) power situation to begin with where there were the colonial governors (both domestic and english appointments, multi class democratic assemblies, colonial outposts, indigenous power formations, French holdings... that was rife with contradictions. The mercantile grievances wouldn't have had traction without that.