Last summer, the 19-year-old made such an impression in Asia and Australia that David Moyes promoted him into the senior squad once the season got underway.
"[The tour] is very important. That's where you have a chance to show your qualities and you get your training [base] for the rest of the season," he told the club's official website. "It's good for the young lads to improve over there and show the manager what you can do.
"When I went on tour I knew some of the lads already form the reserves, but I started to learn more about everyone and how the club works."
In the States, United will face LA Galaxy, Roma, Inter Milan and Real Madrid.