It's the incredible level of interwoven left/right, progressive/conservative, urban/rural populations in more or less every state.
More people voted for the current president in CA than in more or less any other state. Yet it is viewed as a "blue" state. The millions of Democratic voters in large cities like Houston or Atlanta may not control their state legislatures, but they are not going to sit by as those legislatures attempt to secede. Rural voters across most states are not going to sit by while their urban-controlled legislatures attempt to secede.
We don't have "peripheral" states here, and we don't have "red or blue" states. We have a mostly urban/rural divide that does not follow state boundaries in any sense at all.
These are niche behaviors. Most Americans live where they live, plan to remain there (with the possible exception of what is left of the trans community in nominally red states, and some women in similar states). If and when the shit truly hits the fan (to the extent that it has not already done so), most Americans will be right where they are now, without bunkers and having filed their taxes.
I’m not talking about how most people are operating. I’m talking about the current thought movements going on and what people are doing because of the times. These are each niche things that are becoming popularized ideas. The divide you’re talking about Red vs Blue is not where strong bonds lie. We can see that from the extreme flip-flopping on Trump by various demographics and the similarities between Maga and Democratic party being built through small disparate demographics. It might take another 5 or 10 years but people will probably largely stop paying federal taxes and put the money into savings or something elsewhere.
Are just those, thoughts. Show me any real statistics that the average family is making hard changes. It's the same rhetoric as "I'm moving to Canada if <...>". Never happens in any meaningful numbers.
I feel like the lesson from other countries is that the military will be the last thing to go. Public funding of everything else will be sacrificed to keep the military powerful, and leaders will be from the military. That will be a complete breakdown of democracy of course.
I do not think it will happen but this is why in discussions about this happening, or historical fiction, typically the places that break off are the ones that were distinct _before_ they joined the US. Any of the 13 colonies, New England as a block having the strongest colonial identity that I'm aware of, Texas, or California generally are where it's assumed to start as those were countries/had identities very much outside of the US while also having economies that might be ok.
But I would still say that the status of lower-48 states is quite different than, say, Belarus and the USSR.
Yes, Nuevo Mexico existed prior to becoming part of the US, but most of the distinctive identity-forming elements of Nuevo Mexico have been lost or significantly diminished (for a variety of reasons).
I know nothing of Hawaii, the situation there may be similar or very different.
The USSR existed for only about 70 years. There were likely people alive at its creation who were still alive as the eastern European states left it. That's a very different scenario than NM (which effectively entered the US in 1848 with the Treaty of Guadalupe Hidalgo).
It won't change until states nominally considered "red" or "blue" actually lose the vast majority of their nominally opposed population (e.g. Atlanta's current population migrates out of GA). Until then, just about every state is a complex mixture of populations with different political alignments and sufficient sizes to make secession extremely difficult if not impossible.