The Portuguese international, whose playing future has been surrounded by speculation, netted twice to give the Spanish giants the lead after Marcelo's opener had been cancelled out by Ramires in Miami.
Despite the uncertainty, Ancelotti hailed Ronaldo as being a crucial player for the La Liga outfit.
"Ronaldo is the man for Real Madrid. He is very important to us," Ancelotti told the club's official website. "I think that if Ronaldo performs, the coach's job is easier.
"He scores lots of goals, is very important and I am happy to be coaching him. He is professional, focused and very motivated.
"We had a good match, especially in the first half, in which we played well and with intensity. The whole team worked well both on the attacking and defensive fronts."
Ronaldo has been linked with a return to Manchester United as well as a move to Paris Saint-Germain.