The first 13 states, plus a few others, were independent entities at some points in their existence. The rest were carved out of US territory. All of those states were never independent, and owe their bit of sovereignty to their admittance to the union on equal footing to the original states. There was a long period of Colonial history that the first 13 states developed in, and those 13 had to unite to expel the British, but getting them all to agree on a form of government for their union was extremely difficult and we’re still suffering the effects today. Michigan, on the other hand, did not have to overthrow their colonial government to become a member of the United States - they instead united with their colonial settlers.
Trying to say that states matter in today’s world is simply saying that state governments have gone different ways with respect to some things, many of which are rather arbitrary. Most community property are in territory first settled by Spain/Mexico, but Wisconsin was not. Why Wisconsin? I have no idea.
As much as there might be some sort of state culture, most of the overall politics of states has more to do with the urban/rural divide. There’s always strong conservative support in rural areas and strong liberal support in urban areas. That the northeast, Pacific West, and Great Lakes are on the whole more urbanized is a product of geography and history, not one of shared cultural roots.
I wouldn’t lightly uproot myself and accept a job that would require to move my residence, but if I had to move, there’s no real reason why I would prefer to move to another place in the same state compared to another place an equal distance away in another state. I don’t know how many people there might even be that would prefer remaining in-state to moving a lesser physical distance, but I can’t imagine any particularly good reasons other than perhaps problems with tax returns if they crossed a state border commuting.
Thus, should all the state governments were to cease to exist and be completely forgotten except as “neighborhood” names, there is no reason to think that the constituent counties of the US would seek to form the same sort of structures that they have now. Perhaps they would form regional governing councils for groups of counties, but I don’t see how you could think that the people that live in them now would favor forming the states as they currently exist, even knowing that they once were grouped together in that manner.
Thus, I don’t see why we should treat states as meaning anything, other than the fact that their admittance to the union was made on par with the original ones. I say we scrap the entire state system, and redraw boundary lines coterminous with county lines, but in different places, and do this every 10 years so that every state has roughly the same population.
Of course it’s not going to happen. But I can hope.