After WW1 why were Americans more afraid of socialism? What was it that made socialism so upsetting after WW1? It seems like before the war the...

I think that what made socialism more frightening to
people after WWI was mainly the creation of the Soviet
Union.

I would point out, however, that I am not sure that
it was the working class after the war that was really most afraid of socialism.  I
think it was more of the elites who did the Palmer Raids and such who were really
worried.

But to the extent that people in general were more
afraid, I do think that it had to do with the creation of the USSR.  Before the war,
socialism was just some idea.  After the war, it was an idea that had driven the
overthrow of the Russian czars and it was the idea that the Soviets were trying to
export to the rest of the world.

So I think people saw it
as more of a credible threat to them after WWI.