It's like 65% a bit so don't bother ;)
For us on the west coast we can appropriate "calexit" or "Cascadia" as progressive propaganda, but I can't speak for socialists elsewhere in the United States. Different material (geographic) conditions may make the "balkanize the US" tactic unpalatable.
Its difficult because there are many people who are transplants in our major cities cause they don't want to live in chudsville or wherever. They still have family in those places. The short answer is that as much as I would love to solve Ohio and Alabama's problems, I would also like to solve the problems of my Kenyan and Indian and Honduran comrades. I have no effective political or economic power on these places. I do have a smidge of influence in my local community so that's what I'm able to look out for.
I could go on but I'll pause here.