The main cause of the Red Scare was the Anti-Communism in the United States. The First Red Scare was about worker revolution and political radicalism. The Second Red Scare was focused on national and foreign communists influencing society or infiltrating the federal government.
1 Additional Answer
The Red Scare occurred in two periods of Anti-Communism in the United States. The first Red Scare occurred between 1919 and 1920 and it was caused by political radicalism and revolution. The second Red Scare occurred between 1947 and 1957 and it was caused by foreign and national communists infiltrating the federal government or influencing society.