I think there is a completely different culture in Britian to that of the USA, if you just take the example of New Orleans you have the remaining 20,000 or so predomenantly Black an Hispanics that live below the poverty line, as quite rightly reported on the news these people are often overlooked.
A by product of this is the crime and gang culture that proliferates in such area's the widespread availability of guns and numbers of drug users and gang members further compounds this hence the capacity to commit crime and create disorder and potentially discourage act of humanity are so so much higher.
The situation of such large pockets of people that live in the USA in this way is not reflected anywhere else in Western Democracies, even given the poverty in the UK this is thankfully (though unsatisfactorily) represented by fewer numbers and less willingness to commit crime even if you look at some of the worst ares's of UK eg East London, Glasgow, Liverpool etc.
Its the scale of the numbers and the embeded feeling of hopelessness in which these people live that magnifies the problem in New Orleans etc.
I saw a programme about LA a short while ago which said the equivilent of a 911 happens every year in terms of gun deaths (3000 in LA alone) yet the government have done little to even police the poverty and crime ridden area's and seem unable or willing to combat the problem. In all approx 20,000-25,000 people are killed by guns in the USA each year, most of them black on black murders. In the UK although our population is about 15% of USA approc 30 people are murdered by gun crime each year.