I've seen this brought up many times before but I disagree completely that American cities' designs are the culprit. I enjoy visiting my family in their "suburban fortresses" out in the Midwest where you have to drive a car to get anywhere. I enjoy it because it gives me a chance to recover from the crippling social isolation that comes with living in a city with roommates, taking buses everywhere, walking around in crowds, and generally being surrounded by people who don't care about you.

The way I see it, the level of community involvement and social interaction in general have almost nothing to do with infrastructure, unless you decide to go full-on hermit in the mountains. It matters what people are in your life, not just how many are in your proximity.