The Army of the Potomac at the Battle of Long Island

What if the Army of the Potomac at its Overland Campaign peak arrived before the Battle of Long Island with five years of supplies?

The displaced army is expected to overwhelm the British locally, while its soldiers' opposition to slavery creates a conflict with the society they have entered.

The question moves the Army of the Potomac at its Overland Campaign strength to the period before the Battle of Long Island, with five years of supplies. The military result is expected to be disastrous for the British, but an advance into Canada is considered unlikely. The discussion then turns to soldiers motivated by opposition to slavery entering an economy heavily dependent on it. Differences in American speech between the two periods would create another difficulty. Those political and social tensions remain unresolved.