Technological and resources difference have not been equally distributed... yet. Historical consequences of past development and imperialism still has a material legacy. However, we are rapidly seeing a transition in which those geographic advantages are being nullified. For example, the growing economies of China, India, and Brazil. There are still, however, problems like the chronic underdevelopment of Africa which is a legacy of imperialism and the continuance of malaria. Diamond goes into this in some depth in his PBS series of the same title.

Still, things are changing. The Post-American World gives us a hint of how rapidly things are changing.

Why do the social discrepancies that Diamond alludes to persist even after technological and resource differences have been nullified to a great extent?