Kilo,
Your problem is that you are only looking at the macro, and assuming that while we participated in the micro, we had no understanding of what was going on outside of our little world.
Most of us in the Infantry have an intimate understanding of what it means to have coalitions, NATO forces and task forces, the differing missions and tasks assigned to them and when. Why? Because when I go somewhere, I sure as hell want to know what is going on, hence the study. I am hardly alone, as KevB and PPCLI MCpl indicate.
ISAF was given a mandate by the UN, but this was hardly a requirement, it was more (IMHO) an attempt by the UN not to appear completely irrelevant and powerless in policing the actions of the participating NATO nations. ISAF was going to happen anyway, whether or not the UN stumbled accross the right decision. As for the US stopping ISAF's exapanded mission, I would hazard that after such "expanded mandate" disasters such as Somalia, all of the Balkans, Rwanda etc, the US chose simply not to have the onerous and indicisive UN "leaders" control the mission over a series of years and decades a la Cyprus. The US wanted results, to show the world that 1) terrorists could be attacked at home and 2) that they were not invincible, and could be hurt - badly, and 3) that the bad guys could not attack the invariably "soft" UN troops, and using the resulting media attention to claim a victory against the US.
As the UN is not in the business of producing any type of result, their offer of a headquarters staff and a few poorly - trained conscripts from struggling nations was declined. This type of military has already failed in Afghanistan once.
As for the US not attacking Afghanistan with all of it's resources, you are probably right. There are a number of possible reasons for this though. 1) A modern military cannot simply throw it's entire weight into motion on a moments notice. 2) to do so would be foolish, because the "tail" of a modern military machine is required to sustain those operations. 3) "Total War" is extraordinarily expensive 4) the type of enemy being fought in Afghanistan is not easily combatted by troops and machinery specifically designed for the European theatre, against a formed, hierarchial western - style military. While the sight of a tank division rumbling around Kandahar would undoubtedly warm the hearts of many, the fact of the matter is that long standing and effective national government, assisted by Light and Special Forces, will do alot more for bringing Afghanistan into the fold of developed nations.
The "insurgency" as it presently exists in Afghanistan is best fought with the practice of simply killing all of those who actively oppose us through military means, and sparing the local populace the trauma of a Fallujah style urban warfare event. If we can do this effectively, Timmy Taliban and Mullah Mike will simply dissapear when they go off to wage jihad against us - providing the best deterrent, and stimulating those who are active politically, in the democratic context. Saturating the nation with US troops would not be effective.