The fall of the Russian monarchy to the Bolsheviks near the end of World War I prompted the Red Scare in the United States and other parts of the world. The idea that the lower classes could rise up and overthrow the government put fear into the minds of middle class and the institutions in power at the time.
Anarchists, looking to spread chaos, had already brought tragedy to American soil when Leon Csolgosz shot President McKinley in 1901. Anarchists began setting off bombs, and a fear of anarchy, socialism and communism began to spread through the Untied States in 1919. Many people were thrown in jail just for expressing their opinions, as civil liberties were suspended. However, as the calendar turned to 1920, the mood lifted, and the country moved on.
It is sometimes difficult from a modern perspective to understand the instability at work during this period. World War I had featured the most grisly combat in the history of mankind, with more than 37 million soldiers killed or wounded, and it had also featured the introduction of biological weapons. Combining this with a growing industrial movement that brought long working hours and unsafe conditions to needy workers created a country that had a number of fears to face. When the tsarist government fell, the unrest that spread throughout the world seemed like a real possibility in the United States, at least for a few months.