There are two weeks left of August and city officials in a number of cities are working to stave off the kind of unpredictable flash mob violence that, worst case, could set off Londonesque street scenes in the US. Last week came the Philadelphia curfew; a couple of other jurisdictions are feeling nervous now. After random gunshots injured three teenagers in Kansas City last Saturday, the city’s youths are under a 9pm curfew. A similar initiative is being debated in Montgomery County, MD.The police don’t really know what to do about all this. Whether it’s robbing a 7-11 or beating someone up, a quick-acting and organized group of young people can stay a jump ahead of the cops.Occasional small outbursts are a problem; having a flash mob metastasize into a riot would be a catastrophe. As summer turns toward autumn, the weather cools and school days begin, law enforcement can start to relax. However the problems in our cities remain much more acute that most Americans realize.Many American whites think race relations took a decisive and irreversible turn for the better when President Obama took office. Many Blacks disagree, and a new Gallup poll shows how differently American Blacks and whites view the current state of civil rights in the US. 59 percent of Blacks say the government needs to do more to improve the social and economic condition of African Americans, compared with only 19 percent of whites.Not to get out on a limb, but it doesn’t look to me as if the House of Representatives is going to be passing any new civil rights legislation or big urban spending programs for the next couple of years. It also doesn’t look as if the economy will be creating enough jobs in the inner cities to bring youth unemployment down.This is not a recipe for joy. The economic downturn has seen riots across much of Europe. There is nothing in America’s DNA that gives us a pass.