Eight minutes into first free practice for the inaugural race weekend on the streets of Las Vegas, Sainz suffered huge damage to the chassis, floor and power unit of his Ferrari after ripping up a concrete frame of a manhole cover on the iconic Strip.
In a separate incident, Alpine's Esteban Ocon also suffered extensive damage, prompting a chassis replacement.
The Sainz incident caused a red flag, with the session soon abandoned as track workers were required to check every manhole cover on the 6.2km street layout, with discussions taking place to extend Thursday night's FP2 instead.
When asked to comment about the damage to Sainz's car, team principal Vasseur said: "The situation is that we damaged completely the monocoque, the engine the battery. And I think it's just unacceptable.
"We had a very tough one. This will cost us a fortune. We f*cked up the session for Carlos. We won't be part of the FP2 for sure, we have to change the chassis.
"Okay, the show is the show and everything is going well but I think it just unacceptable for F1 today."
The incident caused a major disruption to the first day of running, but could have ended a lot worse having taken place on the fastest part of the circuit, a 1.9km flat-out romp down the Strip.
Early investigations by Ferrari concluded that Sainz's seat had also been damaged by the thump.
When asked if he felt F1 had its priorities straight after hyping up its glamorous Las Vegas return only for it to be plagued by teething issues involving the safety of the actual circuit, Vasseur wanted to keep both topics separate.
"We don't have to mix everything. I think that the show is mega and I'm very happy with what Liberty [Media] did around the race. And I think it's a huge step forward for F1 one," he replied.
"We have to separate what is the show and the sporting side, and the show is mega. But it's not because we are doing this that you don't have to do the job on the sporting side."
McLaren team boss Zak Brown also thought it unfair to suggest the series has cut any corners to try and make the event happen in a compressed timeframe.
"I think first of all, anytime you have an incident, first we've got to fix it," he added. "And then look back and go: 'How did it happen?', whether that's a track issue or a problem you have with your car or whatever the case may be.
"I think it would be unfair and quick to judge that corners were cut. This has happened before.
"I don't think it's because effort wasn't put in or corners were cut. It's just somehow they got it wrong.
"Right now we just need to focus on fixing it. I'm sure it was an engineering related issue that they'll get solved."
