Well, technically, the UN is still presiding over the situation, so that precludes European nations from sorting it without having a mandate from the UN to do so, something the US would be likely to block since it would give carte blanche to the Russians by virtue of proxy control of other Baltic states (just as Russia is blocking overtures in the other direction), so that one is out. Many of those newly independent states may have declared independence from Russia's old Soviet control, but they are still spiritually more in tune with Russia than anywhere else, and they can see which way the wind blows just as well as anyone else too (one look at the block voting on something as trivial as the Eurovision Song Contest will confirm the truth of that). So with that in mind, if for example, you asked the EU to try and sort it instead, they'd spend ten years trying to decide where to have an initial fact finding meeting about the thing, and then another ten years working out the seating plan at that meeting, because the individual countries of the EU are also not averse to having fingers in pies too, so they are not likely to easily reach a conscensus on matters either.
But, joking aside, this is a problem that has been around since the year dot, because we are talking about the region which was traditionally the crossroads of Europe during the days of the Holy Roman Empire (both strategically and culturally), and so you are also talking about cultural clashes and differences in even fundamental views on life as well, before you even get to any race issues. Then as now, the region is a hotspot for the clash between muslim beliefs and more traditionally 'western' religions, and is of course still the crossroads of Europe as far as many immigrants who come via Italy to Europe proper see it, which of course is part of why Russia was backing the Serbs in the first place, as it was seen as another front in defending against such incursions, which of course was why the US was keen to come down on the other side, to make life harder for its traditional Cold War enemy and so on ad infinitum. So all that adds to the complexity of any US involvement clashing with Russia's co-operation with the US and other western nations in the 'war on terror' or at least its appearance of cooperation on the war on terror.
When you think about all that, it's not hard to see why there is an impasse, there are a lot of fingers in pies, for a lot of reasons, and as ever, the people on the ground are the ones who end up suffering.
Incidentally, I was training a woman from Serbia on Photoshop just last week (she was very nice - Ivana, her name is), and we were joking about national traits. She mentioned that the Brits were notorious for going on drunken rampages when abroad (she had worked in Greece for a while - a typical cheap package holiday destination for British louts), but then quantified that by saying 'Don't worry, that's not meant to be an insult, after all, we Serbians have the reputation of stealing anything that isn't nailed down! and that's a fairly accurate assertion'. So if even she is prepared to admit they are trouble, what does that tell you?
Chock