The two Manchester clubs are the latest to hit pre-season action and both needed just one goal to kick off their tours with wins.
Sami Nasri scored a volley just four minutes from time to give Manchester City a win in Melbourne on the opening match of their tour.
The game was the first time that City had met their sister club Melbourne and it was decided late on and in some style, Nasri chesting down Bruno Zuculini's cross before lashing a perfectly struck volley high into the net after 86 minutes.
Man City now face AS Roma on Tuesday and Real Madrid on Friday.
It was a perfect start to his Manchester United career for Morgan Schneiderlin who scored the only goal of the game to start off their American your with a win.
Schneiderlin was one of four debutants for the Reds on the night with Matteo Darmian, Bastian Schweinsteiger and Memphis Depay all enjoying their first run-outs in the red shirt.
The only game came after some neat play from United which led to the ball falling to Mata on the right wing and he crossed to the far post where Schneiderlin rose to loop home a header.
Louis Van Gaal "It is our first 45-minute game. I wanted to see our defensive organisation and that was the main aspect. We didn't give a goal away, only one or two chances, so I am satisfied about that. We played like a team and [Club] America was very handy with the ball, all of the players were very aggressive and quick, so it was not so easy.
"All of my players have done the function of what they have to do in our philosophy, so I am happy and satisfied. We have won so in the tournament we are still in the race."