Leclerc and Lewis Hamilton were excluded from the race results after the FIA found that the floor planks underneath their cars had suffered excessive wear.
It meant that Leclerc lost out on sixth at the Circuit of the Americas, compounding a frustrating race for the Ferrari driver.
Speaking ahead of this weekend’s Mexico City Grand Prix, Leclerc refused to make excuses for his DSQ.
“Honestly, it was a complete surprise,” Leclerc said. "Because on Friday when we changed the car, there was zero wear, so it's not like we were touching anywhere.
“Then you get to the race and obviously, things haven't changed, but we were illegal.
“Rules are rules, and they need to be respected, so it's not an excuse to say that on Friday we were fine. We need to look into it to try and better anticipate what is going to be the wear.”
Leclerc revealed that Ferrari were still not concerned by the level of wear after the Saturday sprint race.
“Also on the Saturday night, we could see more or less where we are touching and we thought there was still plenty of margin,” he added.
“And then we finished the Sunday and it was a big surprise, so we are still in the analysing part of where exactly did we wear the plank more than what we expected.”