Originally Posted by ZenGum

The UN is not effectively stopping war and human misery caused by international non-cooperation. It may be limiting these ills a little but isn't doing a very good job.

But why do people therefore conclude it should be abolished or abandoned?

My tap isn't pouring enough water into my sink, therefore I should turn it off and give up.
No, my tap isn't pouring enough water into my sink, therefore I should try turning it on harder, and if that doesn't work, get a new and bigger pipe put in and use that.

Having an effective planetary government would, I believe, be a good thing if it were done right, for the same reasons local and national governments are in general good things. True, the UN isn't delivering what we want from a global government. So what we need to do is make it work better. It might take substantial reform. It might take starting over from scratch. There are many issues and problems and dangers. But I can think of few things more important for human civilization than this.