I’m not smart enough or arrogant enough to think that I know what will work. So please have a bit of grace with me as I am sure I’m bound to cock up this answer in myriad ways, but I’m working on broad strokes here. I’ve arrived at this place because the concept of federalism has failed and the lizard people in DC exercise more and more control over what goes down in the individual states.
A good baseline to start with is imagine Balkanization without so much ethnic cleansing.
Obviously AK and Hawaii would go their own ways.
I’d figure the left coast would do its own thing, though I would expect some wars of secession as much of the rural areas would do their damnedest to join the new countries formed by the neighboring states. Large chunks of the land mass of those states want nothing to do with the coastal cities, but those cities absolutely must retain the ag areas if they don’t want to starve to death. This will be a reoccurring theme throughout. It would also be very difficult for the coastal cities to retain control of any territory to the east of the mountain ranges.
Idaho, MT, WY, some or all of the Dakotas and Nebraska would likely form a nation. Biggest question there is what the Native American tribes will choose to do. Do they go fully independent? Do they align with the states for economic reasons? I cannot even begin to guess. Which leads me to the next area as it would be dealing with the exact same issue.
Utah, most of Nevada, along with chunks of Arizona and Colorado would become a Mormon theocracy.
The rest of Arizona, New Mexico, I’m not sure. More questions of Native Americans and what they would choose to do arise.
Texas, is of course, Texas. I imagine OK, Parts of NM and even maybe parts of wester AR and LA would throw in with them.
The South would be the South, thought I don’t know how LA would really go. Do they throw in with the South or Texas? I have no idea. I do think that VA could lose a chunk of NoVA to the northeast.
Missouri is a wildcard. Do they go with the south or with the Midwest? Maybe even Montana through MN and all the way down to MO? Some border states between regions are a bit of a toss up. Especially ones with unique cultural populations.
The Midwest: Minnesota(?), Wisconsin(?), Iowa, I see joining with the rust belt. Illinois, Michigan, Ohio, Pennsylvania (tossup with northeast, maybe split).
Northeastern states would likely fly together (to the relief of the everyone else) with the exception of Maine, Vermont, and New Hampshire. Were a true Balkanization to occur, I think odds are better than even they would seek to join Canadia.
This would cause some serious realignment in how certain cities are made up going forward. The one that sticks out to me the most is Denver. It’s very isolated culturally from the surrounding area. Does it attempt to exert power and influence on where it lands, become an independent city-state, or does it experience a mass outward migration thus returning it to the kind of place it was 50 years ago?
It would absolutely cause massive amounts of migration as folks who maybe could tolerate certain things until retirement (nobody retires and moves to the northeast) find those options disappearing and decide to cut bait.
Like I said, spitballing broad brushstrokes here. I know I’ve clocked up plenty here. I just believe that we are far too big and far too diverse culturally and politically to make things work much longer.