How naive you are. Of course he couldn't ruin America on his own. He was part of a much larger movement to degrade our culture and propagandize for the communists. Again, see "Popular Front".
"The Popular Front sought to enlist Western artists and intellectuals, some of them not party members but “fellow travelers,” to use art, literature, and music to insinuate the Marxist worldview into the broader culture. The murals of Diego Rivera, the poetry of Langston Hughes, the novels of Howard Fast—all exemplified this approach. It’s an irony that communists should seek to change the culture, of course, since Marxism holds that culture is merely a reflection of underlying economic structures, whose transformation will bring about capitalism’s inevitable collapse."
http://www.city-journal.org/html/15_3_urbanities-communist.html
I’m not discounting your point at all about communists trying to do that. I’m asking for an explanation of how Picasso’s cubist period was a part of that when it ended in 1912 and he didn’t join the Communist Party in 1912.