Juan Mata had the ball in the net for United in the 20th minute but the midfielder strayed narrowly offside as he raced on to a superb long pass from Alexis Sanchez.
Reinforcements, you mean players that I would like to buy, that's another thing.
"I would like to have two more players", Mourinho said. "We are not playing here to improve the team or improve our dynamic".
"We are playing just to try to survive and not have some ugly results". He defended his senior players, Alexis Sanchez in particular, and showed little to no concern for the abysmal manner in which they lost.
"We don't have wingers, we don't have strikers. And the poor man is there trying his best with the frustration of someone who wants more".
Mourinho praised Ivorian defender Eric Bailly for stepping in after Smalling had pulled up moments before the game.
Mourinho, whose side were level with Liverpool at half-time before the Reds scored three unanswered goals, continued: "This is not a step for anything, the majority of the payers which played are not going to play some of them are not even going to belong to the squad".
"(Ander) Herrera, (Juan) Mata, Alexis (Sanchez), (Matteo) Darmian, these are the boys we have, they can not give more.
Compounding United's problems, Mourinho revealed Serbian global Nemanja Matic would miss the start of the season after undergoing surgery in Philadelphia to address an undisclosed injury. He came from the World Cup with the injury and the time he had to rest on holiday was not enough to resolve the problem. This is not even half my squad, or 30 per cent of it.
It was a nice way for the Reds to finish up their U.S. exhibition swing as they now travel back to Merseyside before continuing their preparations for the season with a training camp in France beginning next week.
Liverpool manager Jurgen Klopp said Xherdan Shaqiri's debut was "not normal" after the new signing scored a stunning bicycle kick in the 4-1 rout of Manchester United.
Liverpool ended their United States tour on a high with Sturridge and Shaqiri providing a decisive impact as second-half substitutes, Sheyi Ojo's cool penalty helping secure bragging rights and three ICC points in front of a very big crowd at Michigan Stadium. (Mo) Salah played 45, then 45. That set the stage for Shaqiri to bring the packed stadium to its feet eight minutes later with his overhead kick from inside the box off a nice feed from Ben Woodburn.