Those states already have borders and militaries. Also, why does independence mean "closing off economically"?
> Their prosperity is based in large part on integration into the union.
Canada's prosperity is more dependent on the US than california, ny or texas is. Are you saying canada is not a country?
Also, you are forgetting that texas used to be a country and tried to become a country during the civil war.
American states are structured as independent nations. They have their borders, flags, histories. They have their own executive ( governor ), legislative branch, militaries ( national guards/etc ), etc.
Perhaps a better argument would be canada's first "nations" or our native american "nations" dreaming of independence.