I may have strange perspective as I live/work one side of the Atlantic but my wife/home is on the other, but I can definitely say this would not happen in the US, for two reasons (one opinion, one fact)
1) First the opinion: the majority of those rioting are not tax paying, law abiding citizens but those that think hand outs are a right and the country owes them something. This is not a function of 'class' (there are as many white as blue collar youths involved)
2) The normal citizens in the US would have stepped up and stopped it; and here the issue isn't the normal citizens. I have just phoned home to make sure my wife is OK, she says there are riots expected in our town tonight; at the local store they have been told....if there is a riot, let the rioters do whatever they want, don't confront them, clear up the mess afterwards. So who told them this? The local police!
Caspian Blue '03 BA, Union Jack/Stars and Stripes paint, BUBs, Progressive 812s, and lots of chrome