If the Canadian colonies had joined the American Revolution

How would the American Revolution have changed if the colonies that became Canada had joined the revolt?

The conflict would have become a much larger eighteen-colony war, but stronger British access, important commerce, and easier reinforcement in the north make the outcome difficult to reduce to a simple rebel advantage.

Canada was not yet one unified colony, so the scenario adds several distinct colonial societies to the revolt. Their participation would enlarge the rebels' territory and economic base, turning the conflict into something closer to an eighteen-colony uprising. The northern colonies were also commercially valuable and geographically closer to reliable British reinforcement routes. Britain would have a strong incentive and a practical opportunity to fight hard for them. Adding their population to the revolutionary side alone does not settle the balance.