It sounds like there's two arguments/points--whether or not Bradbury was aware of/concerned with McCarthy, as well as whether or not that affected him/his writing. I'm inclined to think both, since he was pretty upset by the book burnings and seemed to have heard of the news abroad. (I am not sure how many Americans--and Bradbury himself--knew about or cared about what was going on, like you say.) And I subscribe to the "no one creates in a void" theory. But this is all just speculation. :P