Aston Villa's finished their US tour having lost all three matches with a late Illian Hernandez strike inflicting defeat on Unai Emery's side at Chicago's Soldier Field stadium.
Hernandez got the only goal when he raced clear before firing into the bottom corner for Mexican champions Club America.
Villa, for whom summer signing Ian Maatsen made a first stat, had earlier almost taken the lead when Leon Bailey's strike hit the base of the post before captain John McGinn also struck the woodwork from the rebound.
But Club America, backed by more of the crowd than Villa, finished the game strongly and secured the victory when Hernandez beat the offside trap and then sent a calm finish beyond 20-year-old goalkeeper Oliwier Zych.