I don't think that the UN could have a beneficial impact on the Middle East situation simply with the removal of America's veto power. The current situation in the UN is that the Arab states, convinced that Israel is evil, pass resolutions which include condemnations of Zionism as racist and other anti-Semitic crap, and the U.S., convinced that Israel is good, vetos any resolution that is viewed as condemning Israel, even when such condemnation is warranted.