Holders Spain will meet the Czech Republic in the Davis Cup final following this weekend's semi-finals.
David Ferrer's 6-7 6-3 6-4 6-2 victory over John Isner gave the Spaniards a 3-1 victory over the USA in Gijon on Sunday.
The world number five has now won all 16 of his rubbers on clay.
Meanwhile, Tomas Berdych's 6-3 6-3 6-4 victory over Carlos Berlocq sealed a 3-1 Czech triumph over Argentina in Buenos Aires.
Berlocq was playing for the injured Juan Martin Del Potro, who pulled out on Saturday with a wrist injury.
The Czechs will host Spain in the Davis Cup final on the weekend of November 16.
