It's impolitic to notice it, but America used to be a lot like this as well. See, e.g., Bowling Alone by Harvard political scientist Robert Putnam (http://www.a

It's impolitic to notice it, but America used to be a lot like this as well. See, e.g., Bowling Alone by Harvard political scientist Robert Putnam (http://www.amazon.com/Bowling-Alone-Collapse-American-Community/dp/0743203046 http://www.amazon.com/Bowling-Alone-Collapse-American-Commun...). One of Putnam's main conclusions: a principal factor undermining social cohesion (corresponding to a decline in "social capital") is diversity. We're constantly bombarded with messages that "diversity is our strength," etc., but you'll note that Japan isn't exactly diverse by our standards. Neither does it face much pressure to allow massive immigration to change that. You may still believe in the benefits of diversity, but there are also costs. One of them is that little kids can't ride American subways alone.