Debast scored in the 45th, Onana put the Red Devils ahead in the 53rd and De Ketelaere converted a penalty kick in the 59th after a hand ball by U.S. captain Tim Ream.
Lukébakio entered in the 62nd minute and beat Turner from long range in the 68th and 82nd minutes to build a 5-1 lead before a disappointed largely pro-American crowd of 66,867 at Mercedes-Benz Stadium, site of a World Cup semifinal in July.
Patrick Agyemang scored for the U.S. in the 87th after Ricardo Pepi took advantage of defensive misplay.
The U.S. lost a home game by three goals in which it scored the opening goal for the first time since an 8-1 defeat to England in 1959, according to Opta.
Belgium extended its unbeaten streak to 10 games and has won six straight against the U.S. since losing to the Americans at the initial World Cup in 1930.
The U.S. had entered with a five-game unbeaten streak that created optimism but was missing several injured regulars.
McKennie put the Americans ahead when he took advantage of Johnny Cardoso’s pick to cut in front of Nicolas Raskin and volley Antonee Robinson’s corner kick past Senne Lammens.
American players debuted jerseys with red and white stripes that resemble a waving flag.
With the roof closed in an air-conditioned stadium, fans booed the water breaks in the middle of each half — which will take place at each World Cup match.
Belgium was missing striker Romelu Lukaku, midfielders Leandro Trossard and Hans Vanaken and goalkeeper Thibaut Courtois because of injuries and fitness issues. The Red Devils play Mexico in Chicago on Tuesday.
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AP soccer: https://apnews.com/hub/soccer