Many eminent figures in US popular culture were in favour of some form of Socialism, or were politically committed to "heretical" points of view like anti-militarism.  This is conveniently whitewashed out of their biographies as taught to school kids, and out of their writings as collected in popular anthologies.  Twain's passionate and scathingly-expressed opposition to US invasion of the Philippines is largely forgotten, as is Paul Robeson's commitment to Socialism and labour rights as well as civil rights for American Blacks.  Helen Keller (another "all American Disney heroine") was an active Socialist.  American textbooks of my generation managed to cover the works of GB Shaw without mentioning his Socialist or vegetarian views!

In American discourse, Socialism is inherently "evil" (wchurchill recently posted something to this effect I believe) rather than merely a flavour or point along the spectrum of legitimate political thought or opinion.  [I forget who once said that the "broad spectrum of American political discourse ranges from the pale greenish blue to the pale bluish green" or wtte.] It's the Scarlet Letter of American discourse, as contaminating as (at one time) was adultery, mixed-race love, Jewishness, divorce or homosexuality.  There is an old fashioned, prudish horror of Socialism, as if it were syphilis.  If any cultural hero was "weak enough to succumb to it" then we don't talk about it in front of the children :-) as that would (a) set a bad, bad example or (b) undermine a cherished national myth by exposing the dirty laundry.

A similar Bowdlerism or revisionism excises surgically from popular consciousness the outspoken antisemitism of Henry Ford, and until quite recently the pro-Nazi sentiments of "Lucky" Lindbergh.  Horatio Alger's fascination for teenage boys can now be spoken of  -- at least by US historians and literati -- in hushed tones;  I think it may many decades before Americans can bear to discuss the socialist speeches or essays of an Einstein or a Helen Keller.

The difference between theory and practise in practise ...