Nicolas Terol claimed a breakthrough Moto2 victory after dominating proceedings at Austin.
Esteve Rabat and Mika Kallio prevailed in a three-way fight for the podium, with Dominique Aegerter losing out by fractions after last-lap contact with Kallio.
Kallio's Marc VDS teammate and poleman Scott Redding meanwhile struggled with tire wear and faded as the race went on. Fifth was still enough to earn him the points lead though, particularly after Qatar race winner Pol Espargaro crashed out on lap four.
Espargaro needed assistance from marshals as he limped away from the scene. He was later able to walk around the medical center, though.
Takaaki Nakagami, second in the season opener, was another casualty. He was fighting for the lead in the early stages but pulled into the pits, and out of the race, on lap seven.
As he hit trouble, Terol hit the front. By lap six the Aspar Suter man had already eked out a one-second gap, and he duly extended that over the remainder of the race. Kallio held second for the majority of the race but came under increasing pressure from Aegerter and then Rabat.
The trio's fight culminated in a thrilling last lap in which Rabat eventually prevailed, but only after Kallio and Aegerter clashed. Redding could not quite join in the scrap, coming home just 0.7 second down on Aegerter.
Johann Zarco, meanwhile, got the better of Anthony West following a race-long scrap for sixth, the pair covered by less than two tenths of a second as they took the checkered flag.
Results - 19 laps:
Pos Rider Team/Bike Time/Gap
1. Nicolas Terol Aspar Suter 42m02.689s
2. Esteve Rabat Pons Kalex + 3.125s
3. Mika Kallio Marc VDS Kalex + 3.175s
4. Dominique Aegerter Technomag Suter + 4.873s
5. Scott Redding Marc VDS Kalex + 5.597s
6. Johann Zarco Ioda Suter + 9.295s
7. Anthony West QMMF Speed Up + 9.440s
8. Mattia Pasini Forward Speed Up + 14.472s
9. Alex de Angelis Forward Speed Up + 16.051s
10. Toni Elias Avintia Kalex + 19.696s
11. Mike di Meglio JiR Motobi + 20.107s
12. Marcel Schrotter SAG Kalex + 23.287s
13. Xavier Simeon SAG Kalex + 23.547s
14. Jordi Torres Aspar Suter + 23.815s
15. Ricard Cardus Forward Speed Up + 33.488s
16. Simone Corsi Forward Speed Up + 35.424s
17. Axel Pons Pons Kalex + 35.532s
18. Danny Kent Tech 3 + 42.451s
19. Yuki Takahashi Tady Moriwaki + 44.314s
20. Julian Simon Italtrans Kalex + 44.688s
21. Kyle Smith Avintia Kalex + 58.964s
22. Ratthapark Wilairot Gresini Suter + 59.940s
23. Steven Odendaal Arginano Speed Up + 1m00.107s
24. Louis Rossi Tech 3 + 1m00.702s
25. Doni Tata Pradita Gresini Suter + 1m08.996s
26. Sandro Cortese Intact Kalex + 1m24.281s
Randy Krummenacher Technomag Suter 9 laps
Rafid Topan Sucipto QMMF Speed Up 7 laps
Takaaki Nakagami Italtrans Kalex 6 laps
Alberto Moncayo Arginano Speed Up 6 laps
Pol Espargaro Pons Kalex 3 laps