Green, a forward with the Oklahoma City Thunder, and McGee, a center with the Washington Wizards, were released prior to the Americans' exhibition game with France later on Sunday at Madison Square Garden.
"It's always difficult to have to pare down and make these decisions because each of these young men have given their time and energy to be part of USA basketball," USA Basketball chairman Jerry Colangelo said in a statement.
"The decision was made predicated on having less players to work with and play during the upcoming exhibition games which will help in terms of our final preparations.
"So rather than bring 14 or 15 players we will now go with 13 because we have yet to make a final determination on 12."
Colangelo must release one more player for the FIBA world championship, which will be held in Turkey from August 28.
(Writing by Steve Ginsburg; Editing by Sonia Oxley)