In 1988 I bought a book written by the International Green Party, telling what they were all about. At the time they were about shutting down the arms race and wanted to eliminate centralized government. Their plan included splitting up North America, much as you describe.Many years ago I read a book called "The Nine Nations Of North America" that addressed this. The author's premise is that North America (he included Canada, Mexico and the Caribbean in this) consists of 9 separate "nations" based on regional culture, often with little in common with each other. Other than Quebec and New England, none of them followed any present political boundaries. The maritime provinces of Canada were included in New England. All have a "capitol", a city the region relates to as being central to it. New York City and Washington DC weren't part of any "nation", but were city-states in themselves.
As someone who's traveled most of the U.S. on either business or personal road trips I can attest to a lot of what he wrote, something I'd picked up on without realizing it.
It was written in the late 70s/early 80s, so a lot of the examples used are a bit dated, but it's still worth a read. The author is Joel Garreau.
Like a dumbass I let somebody borrow it and never got it back.