The Austin track has become so bumpy since MotoGP's 2016 visit that a section of the back straight resembles a supercross layout, Honda's Dani Pedrosa says.
The Circuit of the Americas is hosting its fifth MotoGP event this weekend, with Yamaha's Maverick Vinales setting the pace ahead of Marc Marquez in first practice.
Following the initial 45 minutes of running on Friday, leading riders remarked that the track had become significantly more bumpy since last April's round.
"It's crazy bumpy," Pedrosa, who set the seventh-fastest time, said.
"We have quite a few spots and the bumps are huge. There are two points that are quite strong. It's not a good feeling.
"[There is] one big one on the way into braking at Turn 1; before Turn 6, a big one.
"Turn 10, going down, a lot [there], and then on the back straight, where we move to the left, there is like a whoop section in a supercross.
"It's massive. Very difficult. At the end of the track, Turn 17 and 18, also."
Pedrosa said the bumps were complicating Honda's quest to pair its new engine with MotoGP's control electronics.
"These electronics we're using are not designed for this, they are designed for a flat track," he said. "Let's say a perfect asphalt.
"When you have the bike jumping and the wheel is spinning because there is no contact, the bike will automatically cut [the power].
"And because the spinning is so fast, the cut will be so aggressive. There is no way you can cope with it."
Ducati pair Andrea Dovizioso and Jorge Lorenzo finished third and sixth in first practice, with the bumps also hurting a package on which they are chasing front-end grip.
Dovizioso emphasised that the bumps were "everywhere" around the 3.427-mile layout.
"The track is very bad compared to last year, with the bumps," he said.
"It's like Argentina, for us it makes a big difference.
"But this is the situation for everybody and we have to work from that.
"On the back straight there is six big bumps, you have to hold the bike until braking."