Jefferson (or one similar to it) is the most realistic, as it was actually going to be put up for a referendum... But then WW2 happen, the idea got delayed and then shelved.
Splitting California into multiple states isn't impossibleeither , but it'll require a different type of admission compared to OTL for a split to be made early. Best choice would be for an Earlier Cali, and the stronger Slave States demand the southern part become a slave state.
Cuba, of course, was sought after for decades as a state, so it's hardly unrealistic (though many will complain about cliche).
Baja California was sought after after the Mexican-American War. It only wasn't pursued as Nathaniel Trist, the negotiator, unilaterally gave it up as he felt the US was being too imperialistic. Get a different negotiator, and the US has Baja at least, though I imagine the northern border likely includes San Diego...
Sonora is definitely possible. As is Chihuahua (though perhaps not "that" Chihuahua). However, looking closely, if you combine Sonora/Baja Arizona/Chihuahua, you roughly get the proposed Gadsden purchase alternate that Senator Forsyth proposed in 1857.
Superior could have happened, had it remained a territory and Michigan got the Toledo Strip. Though, it's possible it could have just folded into Wisconsin instead.
Southern Illinois/Little Egypt/Polypotamia is definitely a curious what-if, but it would have required alternate free/slave state dynamics to occur.
West Florida, I'm actually cagey about - The whole point of Alabama/Mississippi's OTL borders was to provide sea access to those states. So I don't foresee it, unless west flordia remains out of the US for a large period of time, or it creates a Vermont/Texas style republic that lasts for a few decades, at which point there is a large enough sense of commonality that West Floridians don't want to be split up.
You can divide up the Midwestern states in many ways, but I don't think you can make them much smaller than they were OTL without more immigration to the US, as they would have low population.
As it is, the Northern Marianas alone (or Samoa alone) would be too small to be a state, I feel. I think that the best way to have them be states is for All of Micronesia to become one state, and both American and West Samoa united to become a state as well. Then the population threshold could be closer...
I'm surprised Plymouth isn't shown; it was a separate colony from Mass. longer than Rhode Island and Providence I believe. Either way, another small New England state akin to Plymouth is certainly possible.
Also surprised North Colorado and West Maryland aren't shown, as those are two recent separatist movements in the US...
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Missing alternate states not pictured:
Inevitable Canadian Annexation, Greenland, the Marquesas Islands (first Pacific Islands US had claims to), Kamchatka/Chukotka, Pretty much every Central American country + Yucatan, Inevitable Great Britain Annexation, the Canal Zone, the Three Filipino States (Luzon/Visayas/Midanao), Pretty much every Caribbean island, sometimes multiple times over. Inevitable Australian Annexation, South Kyushu, Okinawa, Taiwan, Guyana (I hear there's actually a fairly decent sized movement here for this...), Albania, Denmark, and Israel
Feel free to add to the list.
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Also, North Carolina obviously best state. We're the only state that only "gains" territory.
Though I STILL have no idea what that Luneburg thing is about.