How could Soviet propaganda reach the US, or the Americas (excluding Cuba)?
If you are at all interested in the actual answer, The Sword and the Shield is an absolutely fascinating book that answers your question. It was written by Vasily Mitrokhin, a senior historian for the KGB, who brought over thirty years of KGB mission records to the British after the fall of the Soviet Union. He discusses "active measures", which were propaganda campaigns designed to fracture public opinion and cast the US position in a questionable light. This includes really awful and regrettable things, like AIDS being formulated by the US Army at Ft. Detrick, those kinds of lies. Many of these rumors started by agents were spread to CPUSA members, who had members on college campuses around the country.
For a more entertaining version of how the Soviets influenced America and operated on her soil, I recommend watching 'The Americans' on FX network. Set in the 80's during the height of the cold war, the plotlines in the show are based roughly on actual events documented in the book, and from other sources of KGB history.