It's not even just that! Bringing a thing that takes a 10'x20' space to store with you everywhere is unsustainable.

Even a 2000lb Mazda Miata takes up the same number of parking spaces -- one -- as a Ford Excursion, which means it contributes just as much to parking lots destroying walkability as the big SUV does. It also contributes just as much to the "need" to widen roads, since you can only have one car per lane and the longitudinal space is dominated by safe following distance, not the length of the vehicle itself.

The bottom line is that all cars ruin cities, even the small ones. (And before somebody chimes in with "but whatabout Kei cars/compact parking spaces," I'll note that Japan doesn't even let you buy any car -- including a Kei car -- without proof that you have an off-street parking space to store it in, and such spaces are far and few in between in cities since Japan's zoning code is relatively sane. In other words, the total number of cars is substantially limited and that's the saving grace, not the Kei cars themelves.)