Matthew Yglesias provides a very clearsighted case for the UN, and our participation in it, despite all of its flaws(which he acknowledges): "Having rules lets us cooperate in positive-sum ways, or at least avoid negative-sum conflicts. The international system is much the same. A rule-based system would have benefits that go beyond the quality of the specific policies adopted by the rule-making body. The favored American alternative to a rule-based system is a system of unrestrained American hegemony, but this is no more a realistic alternative than is my preferred system of US governance where all the policies wind up being the ones I prefer."

If you look at the UN as a macrocosm of the United States of America, with the attendant disparate levels of wealth, education, resources, religions, and human rights concerns, then it becomes easier to see exactly why we all have a stake in maintaining even an imperfect union.

Obviously this is moot for now. America has currently expressed a preference for abandoning the rule of law worldwide by damning the UN, the ICC, and the Geneva Conventions. At some point the problem will probably be revisited, and this is clearly the argument to put forward.