Wijnaldum, who had struggled with injury and illness in the first weeks of pre-season, was the only one of that quartet to start in a mixed side in New Jersey.
Both sides made a host of changes at the break, with Mane among those introduced for Liverpool, but it was Leroy Sane who struck first.
But Klopp made a series of further alterations on the hour mark, and after some excellent work from Rafa Camacho on the right flank the youngster’s cross was nodded home by Salah.
It was the Egyptian King’s second touch of the game and an emphatic return to form after his frustrating time at the World Cup.
Liverpool were by far the better side in the second half, and were rewarded for their strong performance when Dominic Solanke was bundled over in the penalty area in stoppage time.
Up stepped Mane, who slotted his penalty past Joe Hart to seal the win ahead of Saturday’s tour closer against Man United in Ann Arbor.