I could, just about barely, see nationwide rioting happen, but those casualties are highly unlikely, even if they were only slight injuries. Most riots have a way of feeding on themselves. If potential rioters (which, given the shock of the event, I'd say includes even me, and I'm a self-confessed cowardly bleeding-heart pinko pansywaist Euro-Socialist
) saw on national television that rioting somewhere was 'successful' and went unpunished, they might be more willing to giove it a try themselves. We got to see a similar (though longer duration) effect in Germany after the police went overly soft on a number of attacks on asylum seeker accomodation, which led many others to believe they could get away with it, and the attacks mushroomed. If, thus, for some reason the police did not go out and nip riots in the bud, violent folk elsewhere might well decide to emulate them. Mosques and Arab community centers are easily identifiable targets, as are halal butchers, Arab-style coffee houses and such.
However, most rioters (at least here in Europe, but I doubt America is that different) are not, so to speak, professional users of violence. They seek emotional release, a feeling of having avenged themselves on an imaginary or real guilty party, and in some cases profit (looters do, for one). Many of them talk about 'Death to X', but few actually have it in them to injure or kill someone when the chips are down. Hardly any actively seek to do so. Most of those injuries and deaths would probably result from thrown stones, the trashing or burning of buildings (inhabited or not often makes no difference to rioters) and cases of isolated victims running into groups of rioters (which, after the first day, would not happen much).
I don't think that would make a difference, miond you. The biggest impact of rioting is never physical (take the number of victims and compare them to, say, work injuries or traffic accidents in the same city and they pale to insignificance) but psychological. The picture of 'ugly Americans' partying in front of burning mosques, lynching an imam, chasing Arabs through the streets, perhaps some skinheads 'accidentally' beating a Sikh to death (hey, he had a beard *and* a turban...), and generally terrorising any defenseless Muslims they can find (something tells me any rioters would give the nation of Islam a wide berth) would shock and horrify the world, and much of the nation once it wakes up. If it got bad enough, it might even cancel out any sympathy felt after 9-11, justifying the attack ex post facto to millions in Asia, Europe, and the Middle East.
The most scary aspect of it is that the government might feel obliged to justify the riots somehow, in order to explain inaction and seeming toleration. I don't think any government body (and at best a handful of nutcases in Congress) would actually espouse them, but some waffly talk about 'regrettable excess' and 'understandable anger' could be enough to establish in the public mind that as far as the US government is concerned, there's riots and then there's riots. Welcome back to the fifties.