This is how it could start
California is large enough to be a bioregional sovereignty. If CA started to implement programs like single-payer health insurance coverage and the federal government did not, people could start to identify their citizenry with California instead of the US nation-state. Eventually it would be logical and not all so difficult to secede from the monster. Other states could band together regionally and then, one-by-one, create bioregional commonwealths in North America.