Topic aside, regarding the OP's rant about Americans, it's an offensive word here in the UK as well. Wouldn't be surprised if the entire English speaking world (i.e., the only place this game exists in) was the same.
I could list a lot of UK-based racial slurs against blacks that are more common within British usage than sambo, yet most people would never had heard of them. To be clear, I'm not saying the word loses its horrible meaning because a lot of people don't know about it (directed at 40% of people in this thread), but that it's a very likely possibility that the developers were simply ignorant of its usage and that does not make them ignorant of black history in America or otherwise bad people (directed at another 40% of people in this thread).
Basically, unless someone can prove the developers had prior knowledge of its racial use, all that should come of this is a "ouch, egg on face" situation. Perhaps even an apology by them would be appropriate with the usual "we abhor racism" press release for good measure. It doesn't require a lengthy write-up, an analysis of racial representational equality within videogames (there are a lot of other, better talking points and issues regarding that) or any insults thrown towards the developers.
Short, snappy, quote-able form:
To the anti-PC brigade: get over yourselves and realise racial slurs are still a massive problem within society and a little concious thought over racial representation in videogames is both needed and by large actually lacking right now.
To the PC-brigade: this isn't one of those situations that needs the good fight fighting. It's an unfortunate oversight born out of genuine ignorance and that's about it. Not knowing the term 'sambo' doesn't make someone stupid, it makes them fortunately ignorant.
Everyone else: Kotaku is still shit.