Walking and biking infrastructure and livable/walkable cities/neighborhoods are key pieces to health from youth into old age.
Just because it doesn't now exist in the United States doesn't it mean it can't or should not.
Just because it doesn't now exist in the United States doesn't it mean it can't or should not.
Increase the population of the U.S. to a billion or so, then maybe it will work.
Do you believe that the existence of exurbs and rural areas is what's preventing cities from pursuing less fragile means of transit? Why?
Places where the population density is high enough to have it (New York, other parts of BosWash, Chicagoland) by and large do have it.
The OP was complaining about Los Angeles. Five minutes with Wikipedia and a calculator will demonstrate why mass transit sucks there, and always will. And LA is dense compared to most of the country.