Morgan Schneiderlin got his United career off to the best possible start with the winning goal as United kicked off Tour 2015 with victory in Seattle.
Schneiderlin was one of four debutants on the night, with Matteo Darmian, Bastian Schweinsteiger and Memphis Depay also all being given maiden Red run-outs.
United began brightly and took the lead inside five minutes when the ball fell to Mata on the right wing from a corner and he crossed to the far post where Schneiderlin, signed from Southampton a day before the Tour, rose and looped home a header.
Club America looked to respond immediately and two minutes later Pablo Cesar Aguilar slid in to meet a cross at the far post, but could only put it wide.
At the other end, Mata then went close after good link-up play between Luke Shaw and Ashley Young, with the latter cutting the ball back for the Spaniard, whose effort was well saved.
Wayne Rooney flashed a shot wide after good work from Depay, but the Mexicans still posed a threat and Sam Johnstone (deputising in goal for David De Gea who had a minor injury), smothered the ball at the feet of Miguel Samadio.
The Reds restarted the second half with a raft of changes as LVG stayed true to his word in playing two different XIs, and his much-changed side were on the attack from the off upon the resumption.
Andreas Pereira collected the ball in the area, sold Gil Buron a sumptuous dummy and fired an excellent effort narrowly past the post, while Adnan Januzaj also went within inches of doubling the Reds advantage.
Ander Herrera was next to flash an effort wide, on 70 minutes, when his flicked header from a free-kick rolled agonisingly wide, but Club America weren't going to go down without a fight.
Anders Lindegaard hadn't had much to do up until he was beaten by Alejandro Diaz's close-range shot, but, fortunately for the Reds, his effort struck a post and rebounded wide.
Januzaj looked particularly lively and stung the palms of the Club America goalkeeper late on, but that proved to be the last real opening for United, as LVG's men held firm and ensured a winning start to Tour 2015.
United first half XI: Johnstone; Darmian, Jones, Blind, Shaw; Carrick, Schneiderlin; Mata, Depay, Young; Rooney
Second half XI: Lindegaard; McNair, Smalling, Evans, Blackett; Schweinsteiger; Lingard Herrera; Januzaj; Pereira, Wilson.