All the Zapata westerns are Italian Red Brigade Commie propaganda. You just have to look past that and enjoy them for the music and the machine guns, Bandidos, Federales, and senoritas.
Mao was a force to reckon with. People seem to forget that the US wanted to embrace China in hopes of displacing Soviet influence in the Far East, which is why Nixon warmed up to him. All that aside, the quote was used to set the tone of the movie's backstory about revolutions in general and how they can be more destructive than empowering. As we see with the two lead characters, both men lost their friends and families due to their ideology. One (firecracker) believed in a new nation, the other (Juan) wanted an island unto himself and his family ("My Family is MY nation!"). Both failed.
Cuba actually had a revolution and gained Soviet Aid for decades though, so this not the same thing.
Also, ALL nations eventually fall or change into something else including the USA
Furthermore, Leone wasn't making a docudrama of the Mexican Revolution, even though that's the setting. He's said so in many interviews. His goal was to show the dark side of revolutions that fail.
I am aware of Cuba's history. Fidel Castro was a rube. Shortly after gaining power in Cuba the man was campaigning for donations and enjoying the limelight in New York. Castro committed a serious breach of diplomatic protocol by never asking the US government (Eisenhower) for permission to BE in the country! This set the relationship between the two countries on a downward spiral, as Castro didn't show the proper respect to the President of the US. Castro then turned the Soviet's for support.
Now Castro and his family are no longer in power.
The young people have access to the internet, don't have the same respect for the leadership.