On the eve of World War II, with strong anti-foreign sentiment sweeping the country, the United States Congress passed the Smith Act in 1940. Opposition of democratic ways or opinions were handled like threats targets to get shut down. E.x Nazi and many other communist parties like the U.S communist party got shutdown in 1948.
While alleged Nazi sympathizers were among the first charged under the law in 1943, the Smith Act was most often used as a weapon to target communists with similar opinions to the Nazi or other groups who opposed democracy and had a high level of power or control involving influence on others.
For several years the wartime alliance between the U.S. and Soviet Union protected American communists, but by 1948 Russian-American relations deteriorated when the Cold War began.