Striker Berba, the subject of a summer move after a poor return last season, opened the scoring just after the half-hour in Toronto.
And he set up Danny Welbeck and Tom Cleverley for United's other goals.
£10million defender Chris Smalling had a debut to forget, though, after giving away a penalty.
He fouled Joe Ledley in the box and Georgios Samaras converted from the spot.
United boss Alex Ferguson fielded a strong side in front of 39,000 fans at the Rogers Centre.