This weekend in Austin will mark the start of Sainz's new assignment at the French works team, ahead of a full season with Renault in 2018.
The Spaniard's new teammate, Nico Hulkenberg, is looking forward to it.
"Carlos is a young, ambitious driver," the German told tabloid Kolner Express.
"He's supposed to help us get fifth place in the championship.
"I am looking forward to working with him, because I really get along with everyone."
Sainz, 23, has warned that it could take some time for him to get up to speed in an unfamiliar car.
Yet his cousin and manager, Carlos Elnoro, said that Sainz got a "spectacular welcome" when the former Toro Rosso driver visited his new team at Enstone in the past days.
"The atmosphere was very good and people were very happy to see Carlos, because it was known for some time that he was going to come to the team," he told El Confidencial.
"His arrival is a stimulus for the team before the last races of a long season," Elnoro added.
Sainz himself said that he was impressed by his visit to Enstone.
"The extension at the factory is still under construction but there are already 640 people working there," he said.
"The facilities given an impression of Renault's commitment to be back at the top in formula one. It's another world compared to Toro Rosso."
Finally, it appears that a personal sponsor, Spanish beer brand Estrella Galicia, is set to move from Toro Rosso to Renault.