The 32-year-old fly-half came off the bench to feature as the All Blacks ran in 12 tries for a 74-6 victory in front of a packed out crowd at Soldier Field in Chicago.
Aaron Cruden started the USA clash and, while it remains to be seen who will be handed the No.10 jersey at Twickenham, assistant coach Foster is pleased with Carter's progress.
"Dan came through really well. He had a smile on his face afterwards and the signs are really, really positive," he said. "It was a good first step for him and we're delighted with that.
"I thought he looked half a yard off the pace early on but I think we started to see him get back in to the right sort of tempo as the game finished. We'll make an assessment when it's time this week."