To what extent was US foreign policy effective in containing communism and communist aggression?To what extent was US foreign policy effective in containing communism and communist aggression?
I think that you will probably receive a variety of answers to this question. There will be different levels of validity in each, as well. On one level, the fact that the American vision won out over the Communist vision of the world might be one aspect to address. The perceived threat of Communism did not subsume the world and did not undermine America as a nation. U.S. Foreign policy could be deemed as effective in that the entire world did not "go" Communist. Perhaps, another level of analysis could be launched as to whether the notion of containment against Communism was valid in the first place. The idea of containment was linked to the "domino theory," which asserted that if one nation in a region went Communist, the whole region would follow suit. I think that we can see examples where this was not the case in Asia, Central America, or Africa. In the end, Communism faltered and could not sustain itself. American foreign policy will be seen as instrumental in this, and whether there is a strong correlation between both is something that can be debated.
You can argue that the US was successful in containing communism because (as the previous answer says) communism did not win out in the end. The world is now essentially all capitalist.
However, you can also say that containment failed. Many countries did "fall" to communism. China and North Korea an much of SE Asia became communist. Cuba, right on the doorstep of the US, became communist. If the US had truly been able to contain communism, none of these things (especially what happened in Vietnam and Cuba) would have happened.
The results were definitely mixed. Korea was a draw, so you could say containment worked though the North is still communist today. The US did not manage to maintain a communist-free western hemisphere as Cuba, Chile, Nicaragua and Guatemala had Marxist-leaning governments to different degrees at one time or another. Containment worked well in Europe, but largely failed in Asia.
I think if you look at the example of Vietnam, you have to say that US foreign policy was not successful in containing communism. After all the bloodshed and money to keep the communists out, what did we get for it? Yes communism is not thriving today, but it is not a result of US foreign policy.