He talks about London, New York, Los Angeles, Berlin, and Tokyo. I suspect some of what he bemoans is in fact the suburbanization taking place in many cities, certainly in Los Angeles, and probably in New York.
Much suburbanization in the U.S. was caused by legal action which drove the middle class out of city neighborhoods to independent suburbs with "better schools." What is left in U.S. cities are the wealthy, who are unconcerned with public school quality, and the poor, whose children populate the urban public schools.
A factor limiting upward mobility for the poor is that good jobs for those with limited education and/or language skills have become scarce in developed countries. The U.S. has exported many of its upward mobility jobs to China and elsewhere in the developing world. Millions of Chinese from rural areas have come to the cities to work in factories to produce the world's "stuff." These rural Chinese experience upward mobility, the upward mobility that once existed in the U.S. and Europe.
What we have left in the U.S. are unskilled jobs that pay too little to generate upward mobility. Unskilled people here make hotel beds, wash dishes, drive buses and taxis, mow lawns, wait tables, flip burgers - jobs that cannot be exported. They are also jobs that do not pay enough to boost their occupants onto the upward mobility escalator.
