In the USA, many of the cities grew up around cars. And, those that didn't, still had a lot of wide-open space for building. And we have urban sprawl. It will take a lot to change the car culture.
In Italy, many of the old cities had walls, offering protection to those houses within the walls, and no protection outside of the walls, but that caused relatively dense population areas including narrow winding streets that really are not made for cars.
That is one of the reasons that the popularity of the old Cinquecento, the Fiat 126, as well as the Piaggio Ape (ok, it has been a while since I've been there).
When I was there, there were few one-way streets, and many streets where so narrow that 2 fiat 500s could pass, but anything bigger would end up backing out.
I was staying in a flatter area, but there certainly are cities in Italy where the grades of city streets aren't conducive to cars either.
I could imagine some of those cities completely closing the inner sections to car traffic if they deemed alternative transportation as being sufficient.
However, one of the issues then becomes whether they would support car ownership. Perhaps part of what would need to be built would be big, secure parking garages a few miles out of town, so for those weekend trips, one could go snag the car and head off. Of course train service is pretty good there too.