After equalling Michael Schumacher's 2004 feat a fortnight ago in Abu Dhabi, Vettel made the record his own with another comfortable run at Austin's Circuit of the Americas.
Another triumph in Brazil next Sunday will see Vettel equal Alberto Ascari's all-time record of nine straight wins set in 1952/53, and Schumacher's victory haul for one season of 13.
Behind Vettel, Grosjean equalled the best result of his F1 career in claiming the runner-up spot, coming under attack from Red Bull's Mark Webber late on, but with his tyres giving way the Australian had to settle for third.
Vettel ultimately cruised to his record win, delighting the fans by performing doughnuts at the top of the back straight, and after delivering an emotional message over the radio.
Told he was a record-breaker again, Vettel said: "I'm speechless!"
Only to then add: "We have to remember these days. There's no guarantee they will be forever.
"We have incredible team spirit. I'm so proud of you guys. I love you."
Going into the summer break there was the threat of an intriguing fight to the finish between four, potentially five drivers.
But following the three-week August holiday Vettel and Red Bull have been in a class of their own, aided in part by the change in rules due to come into force for 2014.
With significant resources required for the 1.6-litre turbo-charged V6 engines that replace the current 2.4-litre V8s, teams made a call to focus their money and ideas on next year's cars.
Red Bull, by their own admission, continued to develop this year's RB9 to the detriment of the RB10 as they were expecting far more of a challenge that simply has not materialised.
That has, in turn, led to no-one holding a candle to Vettel and the Milton Keynes-based marque, and the sizzling run of success that has resulted in the 26-year-old German claiming another record.
Webber has threatened occasionally, but in front of a great crowd at the Circuit of the Americas, the Australian suffered his now typical poor start.
Instead of putting Vettel under pressure as the field powered up the hill into the blind left-hander of turn one, Webber dropped back to fourth behind Grosjean and Mercedes' Lewis Hamilton.
On this occasion there was no lap-one charge from Vettel as that was halted by a safety car when Adrian Sutil clattered his Force India into a barrier after clipping Williams' Pastor Maldonado along the back straight.
But once the safety car disappeared at the end of lap four, so did Vettel into the distance, although not with the dominance of some races of late which he was won by 30 seconds.
Arguably the one-stop strategy was instrumental as slightly greater care of the Pirelli tyres was required to ensure the medium in the first stint and hard in the second did not fall away.
Instead, Vettel managed a comfortable gap throughout to Grosjean.
For his part, Webber had one highlight when he passed Hamilton early on and towards the finish put Grosjean under pressure, but as the tyres went off so he had to drop back and collect third.
Hamilton came home fourth, with Ferrari's Fernando Alonso on a weekend when he has battled with headaches and back pain following his incident in Abu Dhabi.
Sauber's Nico Hulkenberg almost claimed Alonso's scalp on the final lap, but had came home sixth, with Mexico's Sergio Perez at the end of a week when he was axed by McLaren.
Valtteri Bottas collected four points for Williams, and his first for the team in his debut campaign, quadrupling their haul for the campaign with eighth.
Mercedes' Nico Rosberg and McLaren's Jenson Button completing the top 10, the latter after passing Toro Rosso's Daniel Ricciardo at turn one on the penultimate lap.
2013 United States GP Final Standings
1. Sebastian Vettel (Red Bull) - +1:39.17.148
2. Romain Grosjean (Lotus) - +6.2
3. Mark Webber (Red Bull) - +8.3
4. Lewis Hamilton (Mercedes) - +27.3
5. Fernando Alonso (Ferrari) - +29.5
6. Nico Hulkenberg (Sauber) - +30.4
7. Sergio Perez - +46.6
8. Valtteri Bottas (Williams) - +54.5
9. Nico Rosberg (Mercedes) - +59.1
10. Jenson Button (McLaren) - +77.2
11. Daniel Ricciardo (Toro Rosso) - +81
12. Jean-Eric Vergne (Toro Rosso) - +84.5
13. Felipe Massa (Ferrari) - +86.9
14. Esteban Gutierrez (Sauber) - +91.7
15. Heini Kovalainen (Lotus) - +95
16. Paul di Resta (Force India) - +96.8
17. Pastor Maldonado (Williams) - +1 lap
18. Jules Bianchi (Marussia) - +1 lap
19. Giedo van der Garde (Caterham) - +1 lap
20. Charles Pic (Caterham) - +1 lap
21. Max Chilton (Marussia) - +2 laps
RETIRED Adrian Sutil (Force India) on Lap 1