I think this question is looking for you to talk about the "Red Scare" (officially, the second Red Scare). A "red scare" is a widespread fear of the spread of communism. One such scare had occurred after the Bolshevik Revolution brought communists to power in Russia in 1917. The bigger scare took place in the USA after World War II, with the onset of the Cold War. The Cold War was the massive tension between capitalist, democratic USA and its allies vs. the communist, totalitarian USSR and its allies. Senator McCarthy was not the only factor in causing such fear in American society, but he stirred up such fears in excessive ways.
A good film you might look for on the subject of McCarthy's fear campaign and how it was overcome is the 2005 movie, "Good Night and Good Luck." The film shows the efforts of journalist Edward R. Murrow to battle against McCarthy's excesses and unfounded accusations.