Olayinka is among 29 players that flew to America on Thursday.
The squad includes two players eligible to represent the Nigeria national teams, with winger Bukayo Saka also selected.
Olayinka, 18, was spotted training with first teamers this week, fueling speculation that he was in contention to be named on the roster.
Nigeria U23 international Kelechi Nwakali, goalkeeper Arthur Okonkwo, winger Xavier Amaechi and fit-again, central defender Joseph Olowu, who have all trained with the first team in the past are not part of the group.
Alex Iwobi is absent, as he is with the Super Eagles at the Africa Cup of Nations in Egypt, where they have qualified for the semi-final stage.
Arsenal will face Colorado Rapids in Denver on July 15, before International Champions Cup games against Bayern Munich, Fiorentina and Real Madrid.
