What term refers to periods of heightened political anxiety about perceived threats from leftist subversives?

The term that refers to periods of heightened political anxiety about perceived threats from leftist subversives is "Red Scares." This term specifically designates two major periods in United States history when there was widespread fear of communist influence on American society and government. The first Red Scare occurred after World War I, in the early 1920s, as fears about the spread of communism escalated, particularly in the wake of the Russian Revolution. The second Red Scare took place during the late 1940s and throughout the 1950s, significantly influenced by the Cold War and exemplified by McCarthyism, where individuals were often accused of being communist sympathizers without substantial evidence.

Understanding "Red Scares" helps contextualize the national paranoia during those times, resulting in social and political backlash against perceived leftist elements, leading to significant impacts on civil rights and political freedoms in the United States.