A caution. Half of the country, roughly speaking, doesn't live in major metropolitan areas, but in the vast expanses between them.
I am concerned that the results of any study conducted only in major metro areas will not allow for the factors unique to that environment versus the factors present (and not) in more rural venues, and as such, any rules or guidelines proposed as a result of those studies will be imposed on rural areas as well without regard for the appropriateness of those measures for the rural environs. One size does not fit all.
This study indicates 21% of Americans reside in rural or small towns.
The cities and "suburban-exurban areas dominate.
Reagan and Nixon came from suburban California. Bush I and II came from suburban Texas.
Carter, McGovern, Clinton came from rural small states.
I don't see a useful pattern.
I have watched suburban sprawl all of my life. (It has been called "White flight," too)
My wife and I have sort of 'surveyed" the West in search of the ideal type of setting. We concluded that small-medium metro areas of 50,000-100,000 are about ideal. Big enough for sshopping, entertainment yet close enough to small town lifestyles and to nature.