Isner earned a straight-set win over Brazil's Thiago Alves 6-3, 7-6 (4), 6-3.
Isner's win came two hours after Querrey earned a 6-3, 6-4, 6-4 victory over Thomaz Bellucci.
The United States is one win away from advancing. Bob and Mike Bryan, the world's No. 1-ranked doubles team, will take on Brazil's Marcelo Melo and Bruno Soares on Saturday, followed by Sunday's reverse singles.
Isner had to overcome a four-week layoff from competitive tennis in winning his match, his seventh Davis Cup competition but the first on American courts. It was Isner's big serve that carried him past the quicker Alves.
Isner finished with 32 aces and had 29 other serves that Alves could not return.
"I always rely on my serve. I wouldn't have such a pretty good ranking if it wasn't for my serve," Isner said. "Going in every match I have to rely on my serve heavily. I wasn't as sharp in other facets of my game. I knew I was going to have to rely on my serve a lot and I did.
"Maybe it wasn't the prettiest, but I'm happy to get through. I littered up the stat sheet for sure. I know I had a lot of aces, but I had a lot of souvenirs into the crowd as well on my forehand."
Isner had a bone bruise on his right knee a month ago at the Hopman Cup in Australia and hadn't played a competitive match since pulling out of his first-round match at the APIA International Sydney in early January.
The lengthy layoff caused some erratic shots, but Isner said the knee was not a concern during the match.
"The knee felt fine. It didn't bother me today," Isner said. "I wasn't thinking about it. That's really crucial. It could be sore tomorrow morning possibly. I don't expect it to be. I'm ready to play on Sunday whether or not it's live."
His best stretch of tennis came near the end of the second set. He trailed Alves 5-4 and had to fight off a pair of set points. Both times he responded with aces before eventually pulling even at 5-5.
In the tiebreaker, Alves jumped out to a 3-1 lead, but Isner won the next four points before closing out the set with successive aces.
He broke Alves in the fourth game of the third set to take a 4-2 lead and held on his final two service games, closing out the match by winning four consecutive points in the ninth game.
Querrey was impressive in his straight-set win over Brazil's top-rated player. He didn't finish with as many aces as Isner, but dominated all 15 of the games he served. He won 45 of the 47 first-serve points that went in and never faced a service break on his serve, winning all but 12 points on his serve in the three sets.
Querrey said he couldn't recall the last time he served as well.
"There's probably been a few, but not many," he said. "The court really helps my serve. When it hits, it really skids away. I mean I couldn't have served much better out there."
Querrey broke Bellucci in the eighth game of the first set and after holding his serve to close out the set, jumped to an early lead in the second set with a break in the first game. Both players then held serve the rest of the set, resulting in a 6-4 win for Querrey.
Querrey matched that feat in the final set, breaking Bellucci in the first game and then holding his serve the rest of the match. He clinched the victory when Bellucci hit a weak backhand into the net at match point.
The wins left team captain Jim Courier happy with his team's position in the best-of-five matchup.
"We're certainly pleased to be in this position," Courier said. "We have a lot of confidence in Bob and Mike. They're going to go out and lay it on the line. It will take a really special effort to beat them."
Defending champ Czech Republic tied 1-1
GENEVA -- Tomas Berdych won his match Friday to bring defending champion Czech Republic to 1-1 against Switzerland after the opening singles.
The sixth-ranked Berdych eased to a 6-3, 6-2, 6-7 (5), 6-1 victory over 289th-ranked Henri Laaksonen on an indoor hardcourt at Palexpo Arena.
The match between Wawrinka and Berdych will open reverse singles on Sunday.
Djokovic gives Serbia a 2-0 lead
CHARLEROI, Belgium -- Australian Open champion Novak Djokovic swept past Oliver Rochus 6-3, 6-2, 6-2 Friday to give Serbia a 2-0 lead over Belgium.
Djokovic was coming off his third straight Australian Open title. Despite the switch from hard courts to slow, indoor clay, the top-ranked Serb dismissed the 127th-ranked Rochus. Djokovic had complained about the court being too wet and dangerous.
Goffin, ranked 50th and Belgium's top player, easily won the first two sets and could have won had he held serve deep in the third set. But Troicki came back and won the tiebreaker, and had no trouble the rest of the way.
Tsonga, France take 2-0 lead vs. Israel
The eighth-ranked Tsonga defeated Amir Weintraub 6-3, 6-3, 4-6, 7-5, and Gasquet followed up with a 6-3, 6-2, 6-2 win against Dudi Sela.
Kazakhstan leads Austria 2-0
The doubles match is scheduled for Saturday, and the reverse singles will be played Sunday.
Seppi helps Italy tie Croatia
Seppi is ranked a career-high No. 18 after reaching the fourth round of the Australian Open.
Italy is looking to win its first World Group series since 1998, when it finished runner-up. Croatia won the Davis Cup in 2005. The winner faces Spain or Canada in the quarterfinals.
Berlocq, Monaco stake Argentina to lead
Berlocq defeated Philipp Kohlschreiber in the first singles match when the German retired with a left hamstring injury while leading 5-4 in the fifth set. Team officials said Kohlschreiber was having trouble walking after the match and it was unclear whether he will be available for Sunday's reverse singles.
Berlocq beat Kohlschreiber 3-6, 7-5, 2-6, 6-4, 4-5.
Information from The Associated Press was used in this report.