I know the passage you mean about Americans not trusting the pedestrian - it describes a town being remade to become a pleasant place to walk... and then needing to be remade, because people didn't want to leave their cars, even to walk 1/4 mile.

How you guys stay slim is beyond me...!

Maybe it's linked to a kind of national paranoia, too? "As long as I'm in my steel shell I'm safe, outside it I might be mugged?"