Paula Badosa won on her Billie Jean King Cup debut as she battled past Kazakhstan's Elena Rybakina in three sets to secure victory for Spain in the Group C tie on Wednesday, while the United States got their campaign off to a winning start.
Badosa, ranked 13th in the world, won 6-2 3-6 6-4 over Rybakina, giving Spain a chance to go into the semifinals if they win over Britain on Thursday.
"It was my first time and I think I enjoyed every minute on court," Badosa said.
In a late Group D match on Wednesday, Coco Gauff and Caty McNally beat Magda Linette and Alicja Rosolska 6-1 6-2 to earn the United States a 2-1 win over Poland, who are without world No 1 Iga Swiatek.
The teams were level before the decisive doubles match after Danielle Collins' opening victory was cancelled out by Linette's defeat of Madison Keys.
McNally said team captain Kathy Rinaldi had told them to enjoy the occasion.
"Kathy kept reminding us to have fun. That's the most important thing for both us, just to enjoy it," she added.
Belinda Bencic led Switzerland to victory over Italy in their opening tie, while Slovakia bounced back from a tough loss to Australia to defeat Belgium and get their campaign back on track.
Olympic champion Bencic, the world number 12, saw off Jasmine Paolini 7-5 6-3 to secure the Group A tie for Switzerland after Jil Teichmann saved a match point en route to her thrilling 6-3 4-6 7-6(5) win over Elisabetta Cocciaretto.
Bencic returned to court half an hour later to team up with Teichmann and wrap up a flawless day for last year's finalists as they beat Paolini and Martina Trevisan 7-6(5) 6-1 to complete a 3-0 sweep.
Earlier, Viktoria Kuzmova and Anna Karolina Schmiedlova won their singles ties to give Slovakia a 2-1 victory over Belgium in their final Group B tie.
Kuzmova scored a 6-2 7-6(7) win over Ysaline Bonaventure and Schmiedlova sealed the tie with a tenacious 5-7 6-2 6-3 win over Maryna Zanevska before the Belgian doubles pairing of Elise Mertens and Kirsten Flipkens won their match.
The competition, formerly called the Fed Cup, was renamed in honour of the 12-times Grand Slam champion and restructured into a format concluding with 12 nations competing over one week for the title.