Kofi Anan reminded us in his recent speech of the mission of the founder of the UN, invoking by name, Franklin D. Roosevelt. Undoubtedly this was designed to appease the US and remind us of our obligation to take the UN seriously.
What Anan failed to remind us of is that the UN was founded by the US only AFTER the US took care of the crazy dictatorial and genocidal menace that threatened to destroy the planet. He of course did not speculate on what the world would have been like had the UN been around before the rise of Nazi Germany. Undoubtedly as France was being invaded they would have fought the US on our interference in European affairs. The US never expected to have to face a maniac who was able to threaten the US, US interests, or indeed the planet.
I can only speculate, but if there was a threat that the US would have suspected that there would be new challenges to US sovereignty, we would not have pressured for an international body which can interfere with our ability to handle it.