(An exasperated reply.)
The US left has been the target of it for a century, since the Bureau of Investigation was founded in 1908. This was followed by the Espionage Act of 1917, the Palmer raids of 1919, and the rise to power of J. Edgar Hoover. 1918 saw a President arrest the leader of his leftist political opposition under the Espionage Act: Democratic President Woodrow Wilson's administration arrested Socialist Eugene V. Debs for opposing World War I. Debs went on to run for President from prison in 1920, gathering 3.4% of the popular vote.
I hear a faint objection: this is in the past. Oh, but it is not. The USA has a long history of political panics against the left: the 1950s, 1980s, and 2000s all saw renewals of those panics, and the expansion of the national security state.