it reminds me a bit of Loveless Land from the
Wild Wild West movie
except
even more implausible
Because it was easy:
"Wild Wild West: Or, The Partition of the United States following the Treaty of Spider Canyon, Circa 1870"
Going in the order in which Loveless described them:
-The thirteen original colonies (which includes Ohio, Kentucky and Tennessee whilst excluding the entirety of Alabama and Mississippi) return to England. I've divided into 3 polities in line with the traditional view among the colonists of how they broke down: the Dominion of New England, the Dominion of Southern America, and the (ironically named) Midatlantic Confederacy.
-Bizarrely, it is strongly implied that Manhattan Island has gone to the "Indians", on the grounds that "they" traded it for a handful of beads. Presumably, since it is being given to the Indians in general and not one specific group, Manhattan is going to turn into some sort of a Pan-Native American city-state. So points for originality. The British are probably going to have to raze the island to evict all of the current "natives", and I am going to guess a significant number of Native Americans are going to be reluctant to leave their traditional lifestyles to live in a big city. Possibly this is a cynical effort on Loveless's part: in addition to being a reward for his henchman Hudson, it could serve essentially as a concentration camp, since his plot of territory has the greatest population of Indians of all of the successor states.
-Florida is returned to Spain, in addition to Alabama and Mississippi, presumably as extensions of West Florida. With that in mind, I indeed restored Spain's West Florida and East Florida territorial division, abolishing Mississippi, and Alabama and leaving a new northern territory, which I am tempted to call "North Florida", but would more likely be called "Alabama" or "Mississippi".
-Mexico (for some reason referred to as "Old Mexico" here) gets back a significant amount of its territory lost in the Texan Revolution and the Mexican-American war restored, save that which Loveless seizes for himself. I decided to re-combine Arizona and New Mexico back into one big New Mexico, since A) that's closer to how the Mexican's historically administered it, and B) it has too small a population otherwise.
-The Louisiana Purchase has reverted to France... this despite the fact that over half of the territory included in it was not, in fact, a part of the Louisiana purchase, and the overwhelming majority of the Louisiana Purchase is now a part of Loveless Land. Regardless, this is in a lot of ways the most insane of all of the land-grants, and these are some fucking gonzo land-grants. It's very difficult to actually access most of it from the coast, and I don't see the British letting the French pass through willy nilly. It's a vast, well-developed territory of an utterly alien culture. I don't think the French will even entertain the idea of bringing most of "Louisiana" into the metropole. So I've instead opted to seperate it into "Orleans", which the government is actively attempting to Francify, and "Upper Louisiania", which is more akin to a protectorate of midwestern states then anything else. There's a possibility they lose it all in the Franco-Prussian War.
-Finally, Loveless Land, or possibly the "Loveless Alliance". A white supremacist (though possibly with "noble savage" views towards the natives, which are curiously common among white supremacists: see "The Education of Little Tree") state run by former slavers. I gave him Alaska, as Russia is not mentioned, and I doubt they would want it back having willingly sold it. In addition, it seems to fit in with the theme of him seizing mostly desolate frontier lands. In addition, I had the Anglo-American border disputes in the Panhandle resolved in Loveless's favor, as I doubt the British would care much about losing some desolate mountains and boreal forests after gaining the fucking preponderance of the United States. Presumably, it's capital will be in "Spider Canyon", a fictional Canyon not far from Promontory Point, Utah.