Vinales claimed pole with a time of 2:00.789, beating rookie Pedro Acosta by 0.328 seconds who was followed by Marc Marquez, last year's champion Francesco Bagnaia and Enea Bastianini.
"We are very confident. Every race, I feel stronger and stronger. I really like the Austin track, it's a circuit that really suits my driving," said Vinales, who won the Portuguese GP Sprint last month.
"We want to have a good race. The sprint race will be very tough but we're going to put on a good show."
Acosta said he was happy to have the second place in the starting grid.
"This weekend, for us it was important to see what we could do on a new circuit, and a fairly difficult circuit like this," he said.
"We'll see in the sprint, we've made changes since Portugal to fight for something. We'll give it a go."
Pramac Racing's Jorge Martin, who is leading the championship after winning the Portuguese GP, finished sixth after crashing twice. Brad Binder, second in the standings, came in 15th.
Vinales wins sprint
Vinales later won the sprint at the Grand Prix of the Americas on Saturday to claim his second straight sprint victory of the season ahead of Marquez and MotoGP championship leader Martin in an all-Spanish podium.
The victory was redemption for pole-sitter Vinales, who also won the sprint at the Portuguese Grand Prix in the previous round but crashed on the final lap of the race in Portimao due to a technical problem when he was running in second place.
"Can I just say I'm dreaming! I want to keep going. The level was amazing... We deserve it," said a grinning Vinales, who became only the second rider to win back-to-back sprints in MotoGP.
Vinales had the perfect start as he shot off the line to take the lead while Gresini Ducati's Marquez moved up from third to second when he overtook GasGas Tech3 rookie Pedro Acosta as soon as the lights went out.
The front-row trio peeled away from the rest of the pack but behind them, Pramac Racing's Martin, who crashed twice in qualifying, moved up to fourth in an attempt to reel them in.
As Vinales continued to increase his lead, Martin managed to elbow Acosta out of the way with five laps to go and set his sights on Marquez.
Marquez, who has won at the Circuit of the Americas seven times, did make a mistake when he nearly went wide but he managed to keep hold of second place for another sprint podium after Vinales took the chequered flag.
Martin ran out of laps to launch an attack but third place extended his championship lead to 24 points.
"We had two crashes (in qualifying) but I was able to make that second row," Martin said.
"It was a tough race, I suffered some issues but we finished on the podium - that's the most important thing."
Acosta finished fourth followed by the second Aprilia of Aleix Espargaro. Ducati's Bastianini came sixth to move up to second in the championship standings.
Red Bull KTM's Jack Miller was seventh and defending champion Bagnaia could manage only an eighth-placed finish to sit 28 points behind Martin in the standings.
