Seles battled against Spain's great Fed Cup veteran for nearly two hours before claiming a 3-6, 6-3, 6-1 victory that gave the United States an unassailable 3-0 lead in the best-of-five championship.
The victory ended Spain's domination of the women's team event and gave the United States their 15th Fed Cup title - their first since 1990.
The Spanish team of Sanchez Vicario and Conchita Martinez were playing their sixth consecutive final, having won the Cup for the last three years, beating the Americans in 1994 and 1995.
But Seles, who became an American citizen in 1994 and joined the US team this year in the semi-finals, has shifted the balance of power.
She easily beat Martinez in Saturday's opening singles and her team-mate, the Olympic champion Lindsay Davenport, was victorious in her match against Sanchez-Vicario to give Seles a chance to secure the tie early.
Sanchez Vicario refused to go down without a fight and the match with Seles was filled with big-hitting Grand Slam final calibre tennis.
When it was over, however, Seles had hit twice as many winners as Sanchez Vicario (42-19) and raised her career record against the Spaniard to 13- 1.
"I was very nervous. I wasn't sure if I was going to be able to turn around but I hung in there," said Seles, who admitted to being far more nervous than she had ever been when playing just for herself - even in the Grand Slams. "All my team-mates were behind me and I just hung in there."
Billie Jean King, the US captain, said: "I couldn't ask for a better team. They've been just fantastic, everyone just pulled together. It's been a tremendous effort on everyone's part."
However, national enthusiasm for the Fed Cup has been running low. Organisers would not provide attendance figures, but fewer than 2,000 turned out at the 9,000-capacity Atlantic City Convention Center, New Jersey on Saturday.
"We wish more people would come out," Seles said. "So few know what's going on that when I was at the hotel people would say: `Why are you here?' And I would be the one telling people why we were here. I don't think that's ever happened."Reuse content