Answer:
Indeed, America was effective in containing the expansion of communism. To understand this statement, we must go back to the Cold War, where the western and eastern blocs, that is, democratics and communists, faced each other in a political, economic, cultural and military contest, led by the United States and the Soviet Union respectively.
In this event, the Soviet Union was supported by the Warsaw Pact, where the nations of Eastern Europe (Poland, Czechoslovakia, East Germany, etc.) supported the Soviets militarily and politically in the event of a conflict with the western bloc. Finally, after the fall of the Soviet Union in 1991, it was demonstrated that America managed to contain and defeat communism, since the countries that were once part of the Warsaw Pact ended up becoming market economies.
Today, very few nations can be considered communist: China (almost transformed into a market economy), North Korea, Cuba, Laos, and Vietnam. This allows us to realize the triumph of freedom over the communist tyrannies during the Cold War.