The Formula 1 World Championship had been settled in favor of Jack Brabham at Monza a month earlier but the US GP still attracted a good entry with Jim Clark and Colin Chapman deciding to race the BRM-engined Lotus 43 despite the fact that his engine failed in the final minutes of qualifying and Lotus had to borrow a spare engine from the BRM factory team. Clark was just a tenth off Brabham's pole position but only a few hundredths ahead of Lorenzo Bandini's Ferrari. Fourth on the grid was John Surtees in his Cooper-Maserati while the BRMs of Graham Hill and Jackie Stewart shared the third row of the grid.

At the start Bandini got off the line better than the others and so took the lead while Richie Ginther managed to get his Honda up to third from eighth on the grid. The order began to sort itself out with Bandini under threat from Clark with Brabham and Surtees getting back in front of Ginther. The battle then saw Clark drop to fourth behind Brabham and Surtees and on lap 10 Brabham took the lead. On lap 17, as the leaders were lapping Peter Arundell's Lotus, Surtees tangled with the slower car and both spun. An irate Surtees pitted but was able to rejoin in 13th place. Bandini dropped out of the race with an engine failure on lap 35 and Brabham gradually managed to pull away from Clark and built his lead to nearly 15secs while the midfield thinned out with the retirement of both BRMs. And then on lap 56 Brabham went out with engine trouble and Clark was left with a lead of almost 30secs over Jochen Rindt's Cooper-Maserati.

No-one else was within two laps of the leader although Surtees was charging hard as he tried go make up positions. He was able to pass both Jo Siffert and Bruce McLaren (who was back with Ford engines after his brief interlude with the Serenissima V8) to claim third place by the finish - a lap behind Clark. Rindt ran out of fuel on the last lap but was still classified second.

It was Clark's first win of the year and the first for the H16 BRM engine.