The Australian was a surprise early elimination from the session after his final flying lap was deleted for track limits.
He had recorded a time of 1:34.265s, which would have seen him progress with the seventh-best time if he’d not run wide at the penultimate corner.
“Most of the lap was good,” he reflected.
“I made a few mistakes in the last sector and obviously the second last corner I just tried to go a bit too fast, and this is the result.
“It’s a shame, but if there’s one good thing about Sprint weekends it’s we have another shot tomorrow.”
Neither Piastri nor Norris looked especially comfortable in the car, during Free Practice 1.
Even still, Piastri was fifth fastest in the sole hour of practice that started the weekend with a time just 0.04s slower than team-mate Lando Norris in fourth.
The Brit, who sits second in the drivers’ championship to Max Verstappen, will start the 19-lap Sprint from fourth.
“It feels okay,” Piastri said of his car.
“Maybe not quite as strong as what it has in the last few races, but I don’t think that’s because we’re weak, I think the others seem a little bit stronger.
“Let’s see. I’m sure we’re still well and truly in the fight.
“It’s certainly not a case of we’re miles behind but it’s maybe a little bit more difficult for us than a few of the other weekends.”
However, starting the Sprint down the order, and with points only awarded to the top eight finishers, adding to his points tally is a big ask.
“We’ll see. It’s going to be tough, definitely to get to the points from where we are,” Piastri conceded.
“But we’ll try. We’ll see what we can do.”
The United States Grand Prix Sprint begins at 13:00 local time on Saturday (05:00 AEDT Sunday).