What evidence did joseph mccarthy present to prove that communists inside the united states did more to spread communism around the world than communists abroad?

I think he claimed to have a list of Communists and their actions, however this was never seen and neither was any other concrete evidence presented. 

Im honestly confused

Just think, why was it effective? -it appeled to critics because it was written well, that made it noticeable to the public including the white population-it was also recognizable to the african americans because it was about their heritage.-it was powerful just keep finding more points and elaborate on them. message me if you need more