On this day in history, President Dwight Eisenhower signed legislation outlawing the Communist Party of the United States.
Eisenhower issued a statement upon signing the act that began:
The American people are determined to protect themselves and their institutions against any organization in their midst which, purporting to be a political party within the normally accepted meaning, is actually a conspiracy dedicated to the violent overthrow of our entire form of government.”
Certainly the U.S. was concerned about plots to overthrow governments. In 1953, the CIA was instrumental in inciting the coup that overthrew the Prime Minister of Iran, Mohammad Mosaddegh. (The CIA acknowledged its role sixty years later.) Mossadegh had sought to reduce the semi-absolute role of the Shah granted by the Constitution of 1906, thus making Iran a full democracy, and to nationalize the Iranian oil industry. Not acceptable, as far as the U.S. was concerned. (It was this action that eventually culminated in the Iran Hostage Crisis of 1979.)
In June of 1954, a CIA covert operation deposed President Jacobo Árbenz Guzmán of Guatemala. The government was in fact the most democratic the country had ever had, but the president expropriated 234,000 acres of land owned by United Fruit, not offering “adequate” compensation to the company. Also not acceptable.
In other words, you could overthrow a democracy if it did not allow the U.S. to dominate the country, but in any event, it would be preferable if you let the U.S. take care of the matter.