i think a more useful question is "what about the existing US economy is what makes it work/effective?" another useful question is "what about other economies make them less effective than the US economy?"
to answer the first question, the US economy works better when it's a freer market. magatte wade gives a convincing answer to the second question about africa when she points out it's generally very difficult to start a business in african countries.
i'm curious about what alternative you are interested in promoting and how. are you against free markets or do you have ideas on how to make markets more free?