However, Kyrgios produced another commanding performance and showed more signs of his newfound ability to produce under pressure, breaking Querrey twice, after the American led 4-1, as he attempted a comeback in the third set.
He then wrapped up the two-hour victory with the last of his 21 aces, comfortably outserving Querrey, who hit only eight.
"It was a tough third set there, I was down a break and obviously a lot of emotions - I was close to the finish line," Kyrgios said. "There were a lot of ebbs and flows, and I knew I hit a bit of a flat patch at the start of the third set.
"But [with coach] Lleyton (Hewitt) on the side, telling me to compete for every point, and obviously the crowd, it's easy to get up out here."
Kyrgios also defended seven break points and stayed focused through moments when he could have previously lost his concentration. Just as he did against Isner, Kyrgios took a while to warm up and fell 3-0 down in the first set, double-faulting twice in his first service game.
But he quickly found his groove, breaking back with a cracking forehand return in the seventh game, before forcing and winning the tiebreak.
Sam Groth will battle Isner in the fifth and final rubber. Australia has not made the final of the Davis Cup since the last time they won it in 2003.