I think instead of looking at conflict zones, you should look at treaties with real effects. Drugs control treaties, for example, are enforced by the UN under US guidance. Every country has banned cannabis (for example) as a result, even countries where such a ban is laughable, where the stuff is endemic and traditional. This leads to problems. Admittedly it's not just the UN.

Also it should be said the UN sets norms for the world to follow which in many areas are extremely valuable.