Spain was a nation-state on the European continent on Earth. Madrid was the capital and largest city in Spain. People or things from Spain were generally described as Spanish.
By the late 2040s, the Optimum Movement had spread to several European nations, Spain included. Spain withdrew from the New United Nations as a result. (Star Trek novel: Federation, Star Trek: The Adventures of Argus: "Nuclear Time")
Patrick Jackson's mother was from Spain. (Kal-Dixas Spaceport)