I keep hearing that Catalonia (relative) prosperity pays the tax bill for the rest of Spain. Perhaps true, but the picture changes when they have to raise an army, Navy & Airforce to protect their new borders. That’s on top of the socialist spending programs of their local government. Unless they can make themselves ‘Switzerland’(Spain controls that outcome) then they are in for a rough stretch, fighting or no.
We are told here in the US that if any state dare claim independence that it would have to purchase the highways, dams, etc. from the Feds if it wanted to break free.
Why would it be any different for the Catalonians?