Parameters:
- The United States of America gains the entirety of Canada (more specifically, the territories of the Province of Quebec, Province of Nova Scotia, Island of St. John, Colony of Newfoundland, and Rupert's Land) during the American Revolution.
- The Constitution of the United States is established roughly on schedule, and in roughly similar form.
- The broad arc of American history follows the same as historically: gradual expansion across the continent westward, and growing sectional differences between North and South.
How might things proceed differently?
Considerations to include: Immediately, there could be an additional 4-6 states made from the Canadian territory by the time of the Drafting of the Constitution, each of which would almost certainly be anti-slavery in their general outlook. Further, the population of the population of this larger US could be roughly 3 million higher in 1860 (presuming said population of these Canadian territories is held similar to history).