Onyenwere averaged 12.7 points and 9.0 rebounds in three wins for USA.
UCLA will open Pac-12 play by hosting crosstown rival USC during the weekend of Dec. 27-29.
USA will begin play on Tuesday vs. Argentina at 7 p.m. PT on ESPN3.
UCLA will play its first five games of the 2019-20 season in Westwood.
The 2019 Pan American Games are set for Aug. 6-10 at the Coliseo Eduardo Dibo in Lima, Peru.
Cori Close and Team USA will begin Group Phase play against Australia on Friday at 10:15 p.m. (PT).