The 41-year-old produced a stunning drive with a damaged car to finish seventh in Austin, having hit the wall at high speed and battled on with broken aerodynamic parts.
But the stewards demoted him to 15th for driving with a damaged wing mirror and then without one as it fell off.
Alpine's successful appeal ahead of this weekend's Mexican Grand Prix means Alonso's seventh place has been reinstated, with the Spaniard taking six points.
"BWT Alpine F1 Team thanks the FIA stewards for convening and reaching a positive conclusion on the matter involving Car #14 from last weekend's United States Grand Prix," read an Alpine statement.
"The team welcomes the decision made by the aforementioned stewards, whereby Car #14 reinstates its seventh-place finish and six points from the race.
"We look forward to continuing our collaborative work alongside the FIA to ensure the racing spectacle is maintained to the highest quality."
The stewards initially upheld an appeal by the Haas team in Austin, an appeal which was submitted after the permitted time limit, leading to Alonso questioning the direction of F1's rules and regulations on Instagram.
"It is an important day for the sport as this decision will dictate if we are going in the right direction," Alonso wrote.
Speaking ahead of the decision at Thursday's driver press conference, Alonso added: "I think I'm very optimistic that we will keep seventh place. The FIA has been very transparent to us this year.
"I think there are a couple of things that are very clear, that they were made wrong from their side. So, as I said, I'm very confident that I will be P7 again in Austin."