Williams will finish this season third in the Constructors' Championship after a double points-haul in Brazil gave them an unassailable lead over Red Bull.
Valtteri Bottas finished Sunday's race in fifth place while Felipe Massa was eighth, moving the team onto 257 points.
And with just one race remaining Red Bull, who are on 178 points, cannot pass.
"We've also clinched 3rd in the Constructors' for the second year in a row. Great job all!" said Williams.
Meanwhile Nico Hulkenberg's sixth place on Sunday handed Force India fifth in the Constructors' ahead of Lotus, a sterling result for the midfield team.
"Great drive by Nico Hulkenberg to get 6th in Brazil n secure best ever 5th position in F1 World Constructors Championship for the team," tweeted team owner Vijay Mallya.
Breaking down their season, Force India added: "19 points finishes, 1 podium, 120 points – 1 race to spare. Time to unveil our brand new hashtag #FifthTheForce…"
On the drivers' front, the top three have been decided with Lewis Hamilton clinching the title in Austin while Nico Rosberg is runner-up after winning in Brazil. Sebastian Vettel is third.