I doubt that many people still hold this uniquely American view,
since Communism has collapsed and the social features in question
still thrive without any assistance from agents of foreign powers.
When one used to point out to the folks who made this argument
that all these were strongly suppressed in most Communist countries
and denounced as forms of Capitalist corruption by them, they
would reply that of course the Communists wanted to keep such
filth out of their own lands--the goal was to weaken ours.
This argument is almost too silly to answer, but it worth noting
that in the very earliest stages of the Russian revolution there
was indeed a good deal of experimental art and music as well as
sexual experimentation. Stalin, however, was far more bourgeois
than revolutionary in his artistic tastes and morals, and suppressed
such modernism as severely as did Hitler on the extreme right.
There were isolated exceptions to this pattern (art and music
in Poland, fiction in Cuba, for instance), but generally where
Communism prevailed there was a stultifying imposition of conservative
artistic standards.
Those who used to make this argument probably knew little or nothing
about this history; they simply associated Communism with everything
they disliked. By the 1950s it was already a joke that conservatives
would call anything new a "Communist plot."
Of course, many experimental artists in Western countries became
involved briefly or for longer periods with Communist movements,
but in most cases they were drawn to them because their rebellious
artistic tastes naturally led them to sympathize with revolution
itself rather than their politics having caused their works to
become more experimental.