Our apartment is in the mountains of Washington state, not on the coast, although the coastal towns of Washington ARE really cheap. I am not talking about the Puget Sound but the actual Pacific Ocean coast. In Ocean Shores, Westport, or even that sparkly vampire area Forks.
On the east coast you can get a cheap apartment in the Florida panhandle in Carabelle or Apalachicola. Heck, we rented a 3 bedroom vacation home on a private lake 5 blocks from the beach for $1600 a month in Carabelle and that was vacation rental prices, not long term lease prices.
I am sure there are cities in Spain that have high rents just as there are places in the USA with high rents.
It has been shown that healthcare in the USA can be as cheap or cheaper than Spain.
So really it is all about where do you want to live, not so much about how this place is cheaper than that place. If you want to retire in the USA, there are plenty of areas where you can do it cheaper than most of the other first world countries.