Due to that evil, vicious, capitalist, anti poor, anti minority, environment raping, infrastructure taxing sprawl, people moved out of their ethnic and coreligionist enclaves for places with more room. In the process, they mingled with everyone else, and as a result, don't have the same kind of peer pressure on ethnic and religious traditions - and only those families interested in retaining certain traditions will pass them down to their children.
Absent contraction back to denser population patterns, this will not be changed - the population is too mixed, and people like the convenience of doing things close to home.
Where I live is as densely populated as ever -- the unfortunate change is from working class to yuppification, which has steadily been forcing the working class out.