It's hard to say this without appearing biased, but I'd say the U.S. for a number of reasons:
- Private weapon ownership and militia culture
- Fierce local/regional nationalism, especially in Texas and the South
- State governments capable of functioning as independent units, with their own economies, budgets, militaries, and judicial systems.
- High population, large country geographically, abundance of natural resources. Many in rural parts could sustain themselves from the land.
- Rocky Mountains and Appalachian Mountains form natural lines of defense, with local hillbilly/pioneer/cowboy populations protecting the agricultural heartland. Any invading army would be stopped at one of these mountain ranges while the interior can regroup and maintain production (similar to the Soviet Union in WW2).
Add in our current economic power, conventional military power, technology/infrastructure, etc. and the U.S. has a clear advantage.
- Private weapon ownership and militia culture
- Fierce local/regional nationalism, especially in Texas and the South
- State governments capable of functioning as independent units, with their own economies, budgets, militaries, and judicial systems.
- High population, large country geographically, abundance of natural resources. Many in rural parts could sustain themselves from the land.
- Rocky Mountains and Appalachian Mountains form natural lines of defense, with local hillbilly/pioneer/cowboy populations protecting the agricultural heartland. Any invading army would be stopped at one of these mountain ranges while the interior can regroup and maintain production (similar to the Soviet Union in WW2).
Add in our current economic power, conventional military power, technology/infrastructure, etc. and the U.S. has a clear advantage.