The United States and communist nations had ideologies and economic theories which were completely antithetical to each other. Western countries, including the U.S., were basically capitalist, a system which to communist theorists, including Marx himself was unfair. From its inception, communists had spoken of a "world wide revolution," in fact the anthem of the communist movement was the "Internationale." This "communist revolution" would be the overthrow of all systems other than communist, by violent means if necessary. Marx himself, in The Communist Manifesto had said:
The Communists disdain to conceal their views and aims. They openly declare that their ends can be attained only by the forcible overthrow of all existing social conditions. Let the ruling classes tremble at a Communistic revolution. The proletarians have nothing to lose but their chains. They have a world to win.
Although many interpreted Marx's words as symbolic, many early communists both in the United States and elsewhere were anarchists. The result was the several "red scares" throughout twentieth century America. The situation was exacerbated at the end of World War II when Joseph Stalin openly declared
The war against fascism has ended; the war against capitalism has begun.
This statement, the incessant talk of a world wide revolution, the Soviet refusal to withdraw from Eastern Europe, and the acquisition of nuclear weapons by the Soviets created an incessant fear in the United States of a world war in which the opposing sides were communism and capitalism. A famous newspaper advertisement of the 1950's showed Soviet Premier Nikita Khrushchev with a finger pointed upward declaring "we'll bury you." This fear led the U.S. Congress to add the words "In God We Trust" to U.S. money, and the words "under God" to the pledge of allegiance. Each of these was in response to the atheism of communism, itself considered another element of the threat posed.
America fear communists and see them as enemies because of the idiology that exist between America and communists bloc. As capitalist, America believe in democracy on the side of political while the communist does not believe in democracy as they see the political equality can leads into social classes, they belive in eradicating this social stratification between those who have and those who doesn't have, also in economic field America belives in free trade this aimed to find wider markets, investments but the communist belive that what they do is not fair trade so they more criticised American policy in foreign countries(it's foreign policy). What communist did is to introduced the communist ideology in most of developing countries so as to be able to avoid or try to influence such countries. This at large do not make america happy as we see during the period of cold war, USSR try to give or put the nuclear missile in Cuba which is a neigbour of America and this become a threat to the America. So the exist fear of America towards communist based much in difference in ideological as the communists are the greater opposer in capitalist economy.