So, a lot of scenarios I see on here that have America taking Canada end up with them ending up taking the rest of western OTL USA as well, through various means. But my question is, would American citizens still migrate there? Let's assume that by 1816 America holds all of OTL Canada. They could expand to the Pacific with little to no resistance, thus fulfilling Manifest Destiny without attacking a strong nation. Also, with the Canadian Plains opened up, wouldn't people rather migrate there and keep American liberties instead of moving to a new area but losing American liberties. So, an American Canada could potentially negate Texas and the Mexican Cession completely, IMO. Another side effect, with northern expansion, is that the slavery issue either is solved earlier, or it develops into an East-West division instead.
Thoughts?