I found a very good article by Bill Bryson on this subject. I had a thread on it a few years ago but it tends to be a pet subject and this article nailed home the point. Americans do not walk anywhere anymore. They will use their cars to drive ridiculously short distances....a few houses down the street to visit with neighbors, to a store or gym that is only one block away, etc.
http://www.independent.co.uk/arts-entertainment/brysons-america-why-would-you-walk-1079183.html
http://www.independent.co.uk/arts-entertainment/brysons-america-why-would-you-walk-1079183.html