Belgium dominated the second half as Benteke scored twice in the 56th and 71st minute. Marouane Fellaini added another in the 64th minute.
Clint Dempsey scored on a penalty shot in the 80th minute but the outcome had already been decided.
American goalkeeper Tim Howard came out to deny a chance for Belgium's Romelu Lukaku, but the ball deflected to Mirallas, who finished off a nifty chip over Howard into the back of the net to open the scoring.
Dempsey assisted on the American's first goal off a corner kick as he used his head to knock the ball across the front of the goal to Cameron who headed it home.
Belgium grabbed a 2-1 lead in the 56th minute when American Omar Gonzalez lost the ball to Kevin De Bruyne, who then sent it to Benteke for an easy goal.
Fellaini made it 3-1 with a close-range header in the 64th and Benteke added his second of the game after being set up by Steven Defour.
USA next faces Germany in another friendly on Sunday before battling Jamaica next Friday in a 2014 FIFA World Cup Brazil™ qualifier.