From my geography class:
By 2000, the vast majority of the world’s mega-cities were in the Global South, leading to a dramatic rearrangement of the world’s top ten cities in terms of population size. By 2034, it is widely predicted that no European or American city will be in the top ten.
Here's the thing, we've seen the results of this before. In Manchester England during the Industrial Revolution, the average age of death was just 17 years old.
More people equals a lower quality of life. Of course this means mostly slums and poor living conditions for these countries, but what does it mean for America?