In the wake of World War II, the victors in that war established a de facto world government -- not the United Nations, though the UN was intended to serve as an instrument and forum through which this government could operate.
What followed was several decades of jockeying by the various powers for a relative advantage, an era of proxy wars and standoffs, punctuated by crisis after crisis threatening sudden death for some segment of the world's population. The Cold War ruined one nation after another, left millions to starve or waste away under the rule of various right- and left-wing dictators, while the principals lived in relative (!) comfort and security, far from the battlefield.
At long last, the Soviet Union fell, and the world welcomed what was to be a new era of peace and prosperity.
The problem was that the various killing machines, be they mechanical, political, or human, remained intact. There was no final conflict, no great immolation of all the implements of destruction the Great Powers had built. They lingered, waited, begged to be used. And those whose homes were destroyed in the proxy wars of the previous era, were still left to starve and/or rot, to seethe and hate and wonder why they were left to suffer.
For example, al-Qaeda (a collection of Islamist guerillas backed by the CIA and some friendly neighborhood authoritarians to wear down our Soviet enemy in Afghanistan) now expected to be rewarded with rule over their region of the planet. When it became clear that this was not going to happen, these killing machines turned their attention on us.
When 9/11 happened, and the White House -- occupied by substantially the same political faction of Cold Warriors that had helped build these and many other killing machines around the world in decades past -- declared that a new global war would be required to rid the world of this menace, those who understood what had brought us to this point in the first place scrutinized the actions of the White House, the de facto (as a result of the aforementioned decades of jockeying) headquarters of the de facto world government, for the answer to a simple and essential question:
What are we going to do differently this time, to ensure that this doesn't happen again?
The answer to that question becomes more apparent every day. Interested onlookers, those willing to analyze events critically rather than absorb rhetoric as gospel truth, can see quite plainly what's being done to prevent another recurrence: