The signing from Southampton played the first-half of their preseason win against Everton in Chicago.
He later told the club's website: “I’ve been wanting to play and wear the shirt since I joined. I'm happy to be finally up to the level of fitness to play 45 minutes, and I’m looking forward to continuing to progress.
“I’ve seen the fans from both sides now, having played at London Stadium for both Southampton and Spurs, and now in front of them as a West Ham player here in the US. I’ve always known how passionate they are, so it was great to finally play in front of them for them, and I really enjoyed the whole occasion.
“It was great to be out there with the team, and I’m looking forward to building those relationships. I’m here to compete, but that’s what brings the best out of you and pushes everyone else. If you want to be a successful team, that’s what you need.”