First off, this is not a racial issue, as Russians and Slavs are considered White.
You would be surprised. At least some people proposed that the Russians constitute an 'asiatic people', so there was/is an ethnic component to some of the rivalry between America and Russia. At the very least, some conservatives/reactionaries/nationalists think of the Russians as belonging to a separate class of people, defined by the Slavic languages or Ortodox Church.
These kinds of views are like self-fulfilling prophesies - the more people believe them, the more they become true. I think it's ridiculous to suppose the nation that gave us the Periodic Table of Elements is an 'alien civilization', but the more people believe it, the more they make it true.