Four-time world champion Max Verstappen moved further into the title picture by winning Saturday's sprint race and then clinching a dominant pole position for Sunday's race after Australian Piastri and teammate Lando Norris suffered a costly collision in the sprint.
The Dutchman charged to pole position in qualifying in Austin, Texas, by almost three tenths of a second from Norris as Piastri could manage only sixth fastest.
Norris was no match for Verstappen but will be heartened to have Charles Leclerc, George Russell and Lewis Hamilton between him and title rival Piastri on the grid for the 56-lap race as he seeks to cut the 22-point gap in the standings.
Verstappen's victory in the sprint earlier enabled him to draw within 55 points of Piastri - and 33 behind Norris - after the McLaren pair collided at turn one and were dumped out of the 19-lap dash.
The Dutchman, who has also finished ahead of the McLaren pair at each of the last three races, will likely need more McLaren chaos to fire himself fully into the title fight, but there are still 166 points to play for.
The build-up to the weekend has been dominated by the unspecified "consequences" imposed by McLaren on Norris after the team held him responsible for banging wheels with Piastri in Singapore a fortnight ago.
That minor tap paled into insignificance compared to the carnage at turn one of Saturday's sprint at the Circuit of the Americas as Norris was left with only three tyres on his car.
Starting from third, Piastri attempted to cut back up the inside of his team-mate but turned into Sauber's Nico Hulkenberg and, as a result, smashed into the rear left of Norris' car.
Norris's left-rear tyre was sent careering across the track. Piastri limped on briefly but suspension damage also put pay to his involvement.
Verstappen took eight points for the win ahead of George Russell and Carlos Sainz.
McLaren's decision to involve themselves in the title fight by sanctioning Norris after Singapore, for a first-lap manoeuvre which was deemed legal by the FIA, will prompt questions over what they decide to do after this latest collision.
Many observers, including former world champion Jenson Button, felt Piastri made a risky move - one which ultimately resulted in the papaya pair colliding - which the team say is their only unbreakable rule.
"I think for me it's a racing incident. I was a long way away from the apex and I think the cars behind were going in pretty deep to the corner," Piastri said.
"Could I have done something a bit different? Maybe yes, but that different thing would have been to potentially let two or three cars go by. I think a racing incident is fair."
McLaren CEO Zak Brown initially absolved his drivers and told Sky Sports from the pit wall: "That's some amateur-hour driving by some drivers up there at the front."
Brown later changed his view, taking blame away from Hulkenberg but did not specify who he held responsible.
Norris and team principal Andrea Stella also refused to apportion blame in the aftermath of the sprint, but McLaren appear to be in a muddle of their own making by attempting to police relations amid the heat of a team-mate title tussle.
While Norris managed to scrap back into the front row for Sunday's start, Piastri struggled to find any pace in qualifying.Â
The Australian has just one podium finish in the last three races as his championship lead shrinks.
I didn't really make any mistakes, just didn't feel like I really got into a rhythm for the whole session, just struggled," said Piastri of his qualifying effort.
"We'll go and have a look at why, obviously. But, yeah, that was obviously a battle.
"Obviously, when you don't have the pace you want, it's never the nicest feeling. But there's a lot of opportunities tomorrow... So we'll see what we can do. The weekend is far from over."
