whatever the faults of the UN as an organization, it was created after world war II to avoid conflicts between the great powers and has through its forum and system of agreed international laws, prevented a major conflict between the superpowers. Prior to WWII any country could attack or annex another country without worrying about any repercussions. How many countries have been annexed since WWII?

If the UN failed in dealing with the genocide in Rwanda for instance, it was mainly due to US unwillingness to get involved (in an election year)
and also an unwillingness to accept casualties only a year after SOmalia.

the people who created the UN (and the US was one of the founding nations and strongest proponents) were far seeing people who lived through a global conflict and who knew what the consequences of war would be. They wanted to avoid the old system of alliances and law of the jungle that preceded wwII.

The law of the jungle is precisely what the neocons want. They want to make America the globocop. Which is really what Iraq was all about. Its so easy to beat a 5th rate 3rd world army though. Not likely to happen so easily in a conflict with a modern army.
Trouble is the neocons, have it wrong, first of all they were shocked that no one other than Britain lined up with them on Iraq and second
even with the largest military in the world, the US would be unlikely to support an operation with high casualties (eg more than 10,000)
as well as the high taxes that would involve.

In the end its silly to think that a nation with 4% of the worlds population, and a (rapidly declining 20%) of the worlds economy can maintain superpower status. First of all, the US already has the international prestige, and economic advantages of the US dollar being the main international currency. In the end economic trumps all,
and with china set to overtake the US economy in a 25 years the neocons are dreaming.