Where does this American fear of socialism come from?

From time to time I read about and hear about the somewhat absurd fear of socialism in the USA. And sometimes Americans tend to equalize socialism and communism, which is just silly. I live in Sweden, a country where the biggest party is the social democrats and even if they aren’t in office at the moment, they have been ruling the country most of the time. I am a socialist aswell and I have been voting on them many times.

So I am curious, where does this fear of socialism come from? What exactly is it that Americans think is bad with socialism? Isn’t this “fear” based on ignorance, I mean to think that socialism is the same as communism…?