I thought this quite an interesting article, though it poses more questions than answers them.
A great deal of the disparity would be due to cultural/area attitudes about eating, smoking, physical activity, etc. I would also think that homicide due to alchoholism and gangs would be a factor in individual cities. http://news.yahoo.com/s/ap/20060911/ap_on_re_us/american_longevity
The article also states that the change of life expectancy of 2nd generation Japanese who have adopted a more Western diet is not as great as expected.