Focusing on the number of parking spots is somewhat backwards and hostile to the citizen. The number of spots is the effect of poor urban design, not the cause.

No, it really is the cause. Having lots of parking spaces physically forces destinations to be further apart, which is what makes people not want to walk between them. Moreover, the reason those parking spaces got built in the first place is because they were forced to be by having large minimum parking requirements in the zoning code, not because property owners necessarily wanted them. (You can tell because traditional development patterns, which are what you get when there's no zoning code mandating it be done differently, does not tend to feature large amounts of parking -- even when it was built in times well into the automobile era (including the present day in places outside North America where it's still allowed).

I remember a while back coming across a post about old FHA and/or HUD design guidelines for commercial developments from (I think) 1938. It illustrated perfectly the sort of thing I'm talking about: it literally had side-by-side plan view diagrams with traditional commercial (think "main street" shops with no parking in front, or only on-street parking) labeled "bad" and shopping centers with off-street parking labeled "good." I wish I could find it again.

Make no mistake: the suburban experiment wasn't some kind of "natural march of progress" or whatever. It was the result of deliberate policy choices dictated from the top down by the Federal government.