Adu scored the opening goal in the 34th minute off a pass from Josmer Altidore and then feed Robbie Rogers in the second half to give the U.S. a 2-0 lead. Alexis Sanchez scored for Chile from the penalty spot three minutes after Rogers put the USA two goals up.
"I think it's important for us to play teams like this that pose different problems," said U.S. U-20 coach Thomas Rongen. "One of the problems in the second half for us was to maintain our composure. The result was important obviously against a good team that tied Brazil and Argentina during qualifying, and I was happy with the outcome, but we know that we can improve in certain ways. Possessing the ball and moving the ball a little bit quicker is obviously important as we move forward."
The USA travel to Montreal on Tuesday in preparation for its opening match against South Korea Saturday at Olympic Stadium. The U.S. will also play Poland on July 3 in Montreal and finish group play against Brazil on July 6 in Ottawa.
June 23 in East Rutherford, N.J.
USA 2 Chile 1. Goals: Adu 34, Rogers 77; Sanchez pen. 80.
USA -- Seitz, Ward, Sturgis, Valentin (Sarkodie, 82), Beltran, Adu (Wallace, 82), Szetela, McCarty, Smith (Zizzo, 46), Altidore (Akpan, 82), Rogers (Ferrari, 82).
Chile -- Toselli, Larrondo, Isla, Suarez, Currimilla (Arenas, 46), Medel (Godoy, 46), Vidal (Sepulveda, 46), Carmona, Vidangossy, Cortes (Sanchez, 46), Medina (Grondona, 46).
Referee: Hilario Garejeda (USA).