Lawson will start Saturday night’s race from 15th while Yuki Tsunoda was able to reach seventh, between the two McLarens, in the other RB.
The New Zealander aborted his final lap in Qualifying 2 with his ultimate time proving almost two-tenths slower than he’d managed in Qualifying 1.
“I lost the car in Turn 14, had a big slide,” Lawson said of his aborted final effort.
“But to be honest, we were barely improving… I was a couple of tenths up, but not enough for Q3.
“We were struggling overall on that lap for grip, so I don’t really know why.”
On Friday, both Lawson and Tsunoda went “quite extreme” in similar but different set-up directions after a disappointing opening hour of practice left them rooted to the foot of the timesheets.
It was a useful experiment, as demonstrated by Tsunoda’s qualifying performance, though Lawson suggests the squad perhaps went too far on his own car after he was unable to complete a qualifying simulation in final practice.
“At the end of P3 this morning, obviously we didn’t set a lap, but the lap we were on was really, really strong and the car felt good and we had a good direction for quali,” he explained.
“Maybe we went too far. We’ll obviously look into it but it’s really just making that tyre work and having such little grip on a new tyre versus what we’ve been running on.
“It’s frustrating.”
Low temperatures have been a complaint for all drivers, translating into little grip as they battle to get the tyre into its ideal operating window, with graining also an issue.
“It’s one of the challenges about this this weekend, it’s in these temperatures,” admitted Lawson.
“[It’s] very, very difficult to [protect against graining].
“So that’s what we’re working on for tomorrow.
“I’m sure it’s going be a difficult race.”
RB heads into the Las Vegas Grand Prix eighth in the constructors’ championship, just five points off Alpine in sixth.
However, Pierre Gasly qualified an impressive third while his team-mate Esteban Ocon will start 11th.
Haas, which sits seventh in the teams’ standings, is also represented in the top 10, with Nico Hulkenberg eighth for the American-registered operation, with Kevin Magnussen 12th on the grid.
The Las Vegas Grand Prix begins at 17:00 AEDT on Sunday.
