Goals from Nicolas Otamendi, Raheem Sterling, John Stones and Brahim Diaz secured an encouraging victory in the pre-season fixture in Los Angeles.
However, City boss Guardiola cautioned against overstating the significance of seeing off the Liga and Champions League holders in a warm-up game.
"We won against the team that was the best in Europe two years in a row," he told a news conference.
"It was not important to them. We need to grow and build - Real Madrid are already done.
"Real Madrid never play badly. We were good. Real are always [a] top team, I admire them, like Barcelona."
City lost 2-0 to local rivals Manchester United in Houston last week and face Tottenham in Nashville on Saturday before returning to England for a friendly meeting with West Ham, as Guardiola targets more improvement from his side.
"It is pre-season so like against Manchester United, when we lost, we made some good things," he said of the win over Madrid.
"But you gain confidence playing at this intensity and at this level.
"I'm not talking about winning or losing, the dream is to be more stable.
"In those terms the result is nothing important. The way we try to fight, to play, is most important to our future. I focus my team and players. I want to convince them the best way to achieve targets."
The coach also offered an update on the progress of three players seeking to return to fitness for the season opener against Brighton on August 12.
He said: "David Silva may be ready for the start of the season, but [Benjamin] Mendy has a muscular injury and he needs two or three more weeks, we don't want to take any risks. Ilkay [Gundogan] also is not ready."