United Nations is an international organization. It was established in 1945 for facilitation of cooperation at various fronts like law, human rights, security, economic development, social progress, world peace etc at international level.
It was basically a replacement of League of Nations, aimed to stop wars between the countries and act as a platform for dialogue. However, when we actually see through the history of United Nations, it has actually failed to play its designated role in the world. It does not have any kind of control over the events occurring in the world. In fact it is governed itself by the super powers of the world.
It failed to stop the war in Afghanistan. It also failed to stop the war between Iraq and Iran. It failed to stop the genocide that was carried out in Chechnya. It also failed to solve the Kashmir dispute. It is standing with those who have power.
As far as American is concerned, America exercises its control over United Nations. UN could not stop America from invading Iraq and Afghanistan. Instead US threatened UN to support it. So it is all a game of power.