Not to mention that relations with Mexico, had we purchased that land, would not be nearly as unilaterally cordial.as they have been since the partition of the Louisiana Region.
Maybe so. The Mexican Democratic Republic have been our friends for many years, and mainly because we didn't go and try to conquer them to fulfill "Manifest Destiny" or whatever.
I think the one really bad thing about all this is that it took forever to get rid of slavery, though; Only in 1897 was slavery to be outlawed, and originally over the course of 10 years at that. Only after most of the Southern states tried to secede in March 1902, did Washington change its mind and eliminate the practice for good(the 19th Amendment, signed on April 2nd, 1904, the day of the surrender of Roland Davis's government just outside the CSA's capital, Atlanta).
And then, what of the Canadian Confederation? Would Canada have been the highly successful American-inspired democracy that it eventually became after gaining complete independence from Britain in 1861? Or would it have faced more problems, or perhaps even been conquered, in part or in the whole, by the U.S.(After all, there always have been a few people from Calgary to Toronto who've advocated union with the U.S. at some point or the other)?
@jycee: well, originally, yes, but I'd also like to point out that the border had to be readjusted in the early 1860s thanks to controversies over the original treaty. Eventually, we got everything north of the Arkansas River and the border west of that was set at 36*36' for everything east of the Rockies. However, though, while it may seem like a poor deal on the outside, the Mexican cities that did exist on the Arkansas ended up reaping enormous benefits from far easier trade with the U.S.
OOC: Not to sound spammy, but one of my own TLs, "
A Nation, Divided" deals with the delay of westward American expansion, as can be seen in the link(anybody want to give me ideas? I'll all ears.

).
Also, what should we do with Canada's west? I was thinking about either a Canada with the entire *Northwest(up to 54*40'), or possibly giving some or all of that region to the U.S., as was done in The Story of a Party or Union and Liberty.