These days, in large non-coastal cities, I've heard that it is often other than you would expect. In cities where there are large international airports, fish is flown in daily, to the point where the fish served in nicer restaurants will not be much less fresh than on the coast. The Denver Post article linked below goes into how fish is flown to Denver within hours of being caught, every day.

https://www.denverpost.com/2009/01/26/how-does-fish-get-from...

Shouldn't you be able to expect any restaurant in spain to follow food safety guidelines?

Most seafood in the US is frozen at some point, regardless of if you are near the coast or not. And, yes, this includes most "fresh" fish, which generally just means recently thawed.

There may be exceptions if it is caught locally and in season, but the vast majority of seafood eaten in the US is not local, no matter how close you are to the coast.