The only walkable cities in the US were developed before the rise of the automobile, New York, Boston, Philadelphia, San Francisco, Chicago, etc. Any city with areas that requires you to own a car to participate in civic life is a failure of urban planning. That describes more or less all urban development in the US since WWII.

> And how would these failures not be explained by poor zoning laws in the US?

Poor zoning and land lease dominated urban development are both failures of urban planning, though the mechanisms are different. Walkable, mixed use urban development is the ideal, whether you’re talking about dense neighbourhoods of apartment blocks with ground level retail like central Paris or Amsterdam or decent suburban growth with detached or semi-detached single family homes where people can walk to an area with shops, pubs and restaurants, a town centre.

Car centric urban design makes living without a car a miserable experience, is a cancer on the growth of local communities and infantilises the young by making them dependent on their parents to go anywhere to do anything.