Globally, you can look here: http://www.guardian.co.uk/news/datablog/2009/oct/13/homicide...
The numbers in Africa look bad, but South Africa is really the only place in Africa together enough to do statistics on this stuff. Of course, they also have the highest murder rate in the world (one assumes that other parts would have them beat handily if they could count it all). Jamaica also tops the list in our Hemisphere. The rate cited there for Haiti is half as high as I've seen it elsewhere, but Haiti isn't a great place for accurate data collection, of course.
I've got some estimates for crime rates of African populations in places where they are severe minorities (there's a figure on the internet that claim 80% of London gun crime is African/Caribbean), but it's really hard to be very exact about this sort of thing.
It's a mess of numbers, but there just doesn't seem to be much room for the case that America's problems are special (Brazil, for example, has somewhat similar population demographics, and broadly similar problems).