Car culture has done this. The destruction of regular meeting places that get you to know and trust your neighbours. Now everyone you see is an untrusted stranger.
I think cars are only a symptom of the real issue, which is that the scale of modern society is just too big for our brains to comprehend or handle. I don't think getting rid of cars would necessarily help one cope with the fact that 99.9999% of people you see are untrusted strangers.
It's not the whole issue, but it's the biggest contributor imo. Even in small American suburbs people still don't know anyone because they never walk anywhere and have no local businesses / recreation spots. They all immediately get in the car and drive somewhere else, cut off from the rest of the world.
