You're greatly overestimating the difficulty of living car-less in a city designed for it. Even in all the places you are discussing, people used to do this all

You're greatly overestimating the difficulty of living car-less in a city designed for it. Even in all the places you are discussing, people used to do this all the time in the times before AC was invented. It's true that there are places like Phoenix, AZ, where it's not really possible to survive (or at least thrive) without constant AC, but this is currently the exception even in the South.