Frenchman Benzema opened the scoring in added time at the end of the first-half after latching onto a Toni Kroos pass.
Ronaldo, who on another day could have had a hat-trick, then doubled Real’s advantage in second-half injury time at the International Stadium Yokohama.
Zinedine Zidane’s men will now play Kashima Antlers in the final on Sunday (December 18).
FT: @ClubAmerica 0-2 @realmadriden (@Benzema 45'+2', @Cristiano 90'+3').
— Real Madrid C.F. (@realmadriden) December 15, 2016
WE HAVE REACHED THE CLUB WORLD CUP FINAL! 🙌#RMCWC #HalaMadrid pic.twitter.com/XEDjcg5bxQ