I think you're missing the criticism, which is not just that an armed civil war is extremely unlikely even given everything happening in the US, if it did happen, it would not splinter the US regionally.

The divide here is urban vs rural. There's no way to turn that into a set of successor regions.

If armed conflict does happen, it'll be much more amorphous, terrifying, and random, concentrated in the cities, and resemble things like the Tulsa massacre at a larger scale.