Answer by John Burgess, former U.S. foreign service officer:
I think it's because there are sometimes gross differences between aspirations for the U.N. and its actual effectiveness. Of course, when the U.N. takes a stance that is in direct opposition to national policies, its utility is questioned.
For some in the U.S.—and it's not just viewers of Fox TV, contrary to what some assert—the U.N. seems to be a way to promote values other than those espoused by the U.S. Constitution. Various efforts by the U.N. to impose a global order that would, for example, prevent criticism of religions, are seen as anti-freedom. The fact that nations like Saudi Arabia and Iran would hold positions on Human Rights Commissions seems at least a joke, if not a direct insult to the concept of human rights. U.N. efforts toward an arms-trade treaty appear to threaten U.S. Second Amendment constitutional rights. That's a very hot-button issue in the U.S.—one that transcends political parties.
The U.N. is seen by some as a huge money-suck, too. The U.S. contribution to the U.N. is large—22 percent of the U.N. budget—and some think that money could be better spent, or not spent at all, given the U.S. debt.
There are indeed "black helicopter" folk who see the U.N. as part of a secret effort to force all countries into one New World Order, with a unitary government that supersedes all national governments and their laws. Like those who see the Illuminati behind everything, they can be ignored.
And yes, there are xenophobic and racist Americans who just don't like foreigners very much. They'd prefer to have nothing to do with them. These sometimes see the U.N. as a back-door way of imposing values other than their own.
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