How did the Cold War cause the Red Scare?

A "Red Scare" is the promotion of a widespread fear of a potential rise of communism or anarchism by a society or state ... The First Red Scare, which occurred immediately after World War I, revolved around a perceived threat from the American labor movement, anarchist revolution and political radicalism.

The First Red Scare's immediate cause was the increase in subversive actions of foreign and leftist elements in the United States. Protests began to gain favorable public views of America entering World War I.