Mark Goldberg posts an interesting discussion with James Traub about the role (and possible expanded role) of the UN in Iraq. I'm often more skeptical of the UN than many of my political/ideological peers, but I think it's also fair to say that one of the reasons the UN sometimes struggles with its missions is that it mostly gets called in when a situation is damn near hopeless. That interferes, obviously, with a group's winning percentage.
(I should also note that my doubts about the UN often have been mitigated or alleviated by reading Goldberg's excellent postings at UN Dispatch; there are plenty of UN actions that seem questionable at first blush but are, in fact, perfectly reasonable and productive when explained -- like this, for example -- and if international relations/politics/institutions are of interest to you, well, there's another one for the blogroll.)
Anyway, since I don't think any external actor can do much in Iraq (save perhaps Iran), I don't think the UN is likely to turn things around. However, to be fair, should the UN have more involvement, the goal wouldn't be to make things all better, but to mitigate some of the fallout and atrocities -- a job at which the US is failing. As Traub says,
It is the melancholy destiny of the UN to be called on in the most desperate situations when everyone else has thrown up their hands or nobody else cares. Here is a case where people care desperately, but there doesn't seem to be any path to success. So, this is one of the besetting problems of the UN: it may be called on, then fail, then be blamed. But you can't say "we are not going to try because it will look bad if we fail." That's not how the UN thinks.
Ultimately the US will have to work with international institutions -- and Iraqis themselves -- to mitigate whatever problems can still be reasonably addressed. Fear of looking bad is an unconscionable reason for not doing the right thing -- however popular that idea might be among Republican presidential candidates, for example -- and the absence (or at least reduction) of such fear in non-governmental organizations is a reason for hope that they'll have some beneficial impact in the mid- and long-term.