Will Hutton's article today is excellent (another one on Comment is Free, I'm not sure what's happening today). He explains why the US will remain an economic leader. Traditions of argument and institutions of learning make it a natural leader in "a world where the deployment of knowledge, brain power and problem-solving are the sources of wealth generation."
There are two reasons, that come to mind, why non-Western countries have such a hard time keeping up:
1) Cultural differences
There is something about the Western individualist, adversarial tradition that is particularly productive. Frank and competitive exchanges of views produce the goods. From what I've seen such exchanges are a particularly important part of public, and indeed private, life in the West. To the extent they become a part of other countries' public life it is often associated with Westernisation.
2) Network effects
Good academics like to study with other good academics. Being around others makes it easier for them to establish a reputation (important if you want to advance your career) and bounce ideas of colleagues. That means that an established academic centre can attract new staff far more easily than a new one.