The United States's policy of containment had mixed results during this period. Direct involvement in the reconstruction of Japan and Western Europe prevented those areas from being communist. The United States also assisted anti-communist leaders in Italy and France in their attempts to maintain power. The United States also stood up to Soviet aggression when the Soviets tried to blockade Berlin in order to force the Western powers to give up all of Germany.

On the other hand, there were some marked failures. The United States stood beside Chiang Kai-Shek during WWII as he fought against the Japanese, and they stood with him during the war against Chinese communists as well. Even though the communists were known to be cruel, the Kai-Shek government was notoriously corrupt. Despite US aid, the communists still took China. The United States was able to stop North Korea from uniting the Korean peninsula under a communist flag, but only after a bloody war that ended in an armistice. The United States backed anti-communist regimes in South Vietnam even though the people who lived there hated Diem, the leader the United States backed.

United States intervention in Europe and Asia is a mixed bag during this period. When the United States devoted its full efforts, such as what it did with redrawing the Japanese constitution and the Marshall Plan in Europe, it achieved a successful result in stopping communism. When the United States attempted to roll back communism through covert action in the Baltic states and with Radio Free Europe, things did not go well. The Soviets attacked this incursion into their territory. The United States also fared poorly when it backed leaders only because they were not communists.

The United States was successful when major communist nations proved to be unwilling to go into total war in order to press their advantage, such as when the Soviets backed down during the Berlin crisis and the Chinese communists did not pursue the war after the armistice even though North Korean leadership agitated for years to receive more military aid. The role of anti-communist policeman was new to the United States and it would continue to evolve the role throughout the Cold War.

The policy of containment was successful to an extent, in that it prevented the Soviet Union from expanding its direct sphere of influence beyond its Eastern European backyard. But what worked in relation to Soviet Communism was considerably less successful when applied to the spread of communism in the developing world, most notably in Southeast Asia and Latin America.

In Europe, the United States could count on the support and cooperation of governments who shared broadly similar liberal-democratic values. In the developing world, however, it was a different story. Here, successive US administrations allied themselves with all manner of unsavory regimes to counter the growing threat of leftist insurgency.

In the process, the United States undermined its reputation as the leader of the free world, making it all too easy for the Soviet Union to cite its alliances with neo-fascist dictatorships and military juntas as evidence of American hypocrisy. The United States' ruthless efforts to contain the spread of communism in the developing world handed the Soviets a propaganda gift, thus making it much harder to present the Cold War as a struggle between good and evil.

The success of the U.S. Containment policy is problematic at best. The doctrine, expressed by George F. Kennan, former U.S. Ambassador to the U.S.S.R.  was to literally "contain" Communism, and prevent its further spread. On the ground, it was quite effective. The Berlin Airlift prevented the fall of that city to Communism; and the Korean war prevented unification of Korea under a Communist regime. Similarly, the unification of Viet Nam under a communist government was postponed for a number of years, although it did eventually happen.

The problem is the cost of containment. The policy was a major factor in the eruption of the Cold War and the development of a bipolar world in which every dispute, even among third world countries, became couched in terms of East vs. West. This included not only the Cuban Missile Crisis but the early Middle Eastern conflicts in which the U.S. and Soviet Union supported opposing sides. One must remember that the two Koreas remain officially in a state of war, so nothing was realized. Also, it was containment that led the United States to involve itself in Viet Nam with disastrous results. On another note, the entire arms race and the concept of mutually assured destruction may not have played out as it did were it not for the policy of Containment.

Some of this information is outside the time frame, but you should be able to connect it easily enough. My thesis would be that it prevented the further expansion of Communism to other countries outside the Soviet Bloc; but also led to the Cold War and U.S. involvement in both Korea and Viet Nam.  Hope this helps.