Answer :
The Bolshevik revolution in Russia was the cause of fears in US and led to Red Scare. Red scare was defensive societal response to the spread of communism in US. The Red scare lasted till mid 1920's and led to the suspension of civil liberties as the people were suspected of having ties with the communists. The red scare caused chaos in the United States. It was initiated by senator Joseph McCarthy, who claimed that there were communist working in US to subvert the US constitution from within. Due to this the suspected communists were exposed and purged, blacklisted and their civil liberties were restricted. in US. Hence we can say that the spread of Communism in US was one of the major concerns of US.
