If it happens (and I don't think it will), that's the way it will be. If the country breaks up Hawaii will go its own way. Probably Alaska will too.
People who think other states would join up with Texas are dreaming. There would just be too much struggle for supremacy. Either Texas would break up into other states or it would absorb them. The rest of the Plains states, say, wouldn't want to just be the tail to a Texas dog.
It would be the same way with California. No way would Arizona or Nevada or Utah join up with them. California might break in two, and each part might join up with other states, though.
Speculating about this is a little embarrassing, but I don't think the Russian professor understands America that well. Kentucky and Tennessee wouldn't end up in the same country with Connecticut and Massachusetts. Montana and Idaho and Utah and Wyoming would be more likely to end up together, rather than divided between rival countries.
But the point is: a lot of things we take for granted will be lost if the country breaks up. The consequences can't all be predicted beforehand.
I’m not even sure the state boundaries would look remotely like they do today. Such a break-up would involve a lot of conflict.
Natural boundaries would develop, and a lot of the straight line borders we see now would be historical anachronisms.
It would be ugly. And bloody.