There is no reason to think the UN had anything to do with preventing WW3. The thing that prevented WW3, is both the US and Soviet leaders got cold feet about starting it, it had zero to do with the UN.

There is plenty of war, and tyranny despite the UN. As a matter of fact, unless the United States takes a strong interest in pushing for, and funding interventions it doesnt happen.

When it does happen, we are blamed (sometimes rightly, sometimes wrongly) of simply serving our own interests.

I would like to hear one good reason that U.S. soldiers should be tried for war crimes internationally, should someone wish to try and bring charges.

I would like to hear one good reason why we should ever screw ourselves, simply because others in the world think we should.

Guess what, other people in the world dont have fairness and agreement as their highest priority. They have their own agendas as their priority. Not that it should be any different, but diplomacy worked perfectly well for many centuries before the UN, and would continue to work perfectly well after.