Marquez is seeking the three peat on Monday after taking his second straight victory last year at the Circuit of Americas track in Austin.
The 22-year-old Marquez completed his best lap in two minutes, 4.835 seconds in the second free practice session, which took place on a dry track in sunny conditions.
Marquez said he is confident going into Sunday’s race.
“We are positive, as we don’t know what kind of weather we will have on Sunday (US time),” said Marquez.
“The feeling was good in the rain, and I felt well on the dry track. We were competitive.”
He finished just ahead of Britain’s Cal Crutchlow, who clocked 2:05.162 while Italy’s Andrea Iannone finished third in 2:05.190.
Australian rookie Jack Miller (Honda) was down in 19th, posting a time of 2:07.916.
Italy’s Andrea Dovizioso posted the fastest lap of the first practice session which took place on a rain-soaked track.
He finished with the fifth fastest overall time in qualifying, just ahead of Italian compatriot Valentino Rossi, winner of the first race of the season last month in Qatar.
Crutchlow was pleased with his second in practice Friday. He said he had to overcome nerves in turn two after crashing out of last year’s race.
“I spent all day being scared through that corner as it was the biggest crash of my career,” he said.
“We took our time to build up the confidence, but overall I feel quite happy.”
Britain’s Sam Lowes finished with the fastest time in both sessions of the Moto2 practice.
The circuit will return to North America for the Indianapolis Grand Prix on August 9 at the Indianapolis Motor Speedway.