We have reasonably good public transit in many coastal cities already, though of course it can be improved. The problem is the suburban rings that are almost completely car-dependent (I mean, where I live now there are many towns around mine, which is walkable, where you cannot do literally anything except by getting into a car).
We really need to completely reorient the country's physical infrastructure towards density and reducing car-dependence. It is a very big task, and that is part of why when "moderate" Senators claim Bernie Sanders' $3.5 trillion infrastructure plan is too expensive I become angry