While in college, my favorite subject wasn't just politics, but it was comparative politics - the study of political systems from around the world. While I liked the historical component, studying foreign political systems allowed me to study politics without my own personal views getting in the way. So, the following is my view, in general, of the way things are going in Afghanistan.
First off, all countries have two types of identities - a sociocultural identity (called a nation) and a political identity (called the state). Thus, in classical terms, the ideal is to have a nation-state, where the political and sociocultural borders are identical. Most of the countries in Western Europe have this to some degree. The French, for example, live in a place called France, and speak French, and eat French food, and generally are part of French culture. And France, the nation-state, has existed more or less for a thousand years. At the same time, unstable countries tend to have more than one nation within the same state. Yugoslavia, for instance, was a compendium of Serbs, Croats, Bosnians, Albanians, etc., all kept together by Tito's force of personality. When he died, the country dissolved into civil war.
Now, there is one exception to this rule, and that's Switzerland. The Swiss speak a myriad of different languages, practice different religions, and have four or five separate cultures. Moreover, Switzerland is a confederation - the local governments are more powerful, in general, than the national government. This works because the Swiss more or less came together because they didn't want to join any of the surrounding nations.
Like Switzerland, Afghanistan is a multi-ethnic state. It is a mix of multiple ethnic groups, speaking different languages with different cultures. At the same time, Afghanistan the country has existed since at least 1747 - so there has to be some agreement among Afghans that Afghanistan should exist. But the fallacy of Afghanistan is trying to build a strong central government. The only way a country like Afghanistan has a strong central government is if the country has a strong and charismatic leader (like Tito), or is a brutal dictatorship (also like Tito, but also Saddam Hussein, etc.). The Taliban fit the bill, but they assisted Al Qaeda. And, in Hamid Karzai, we have neither a charismatic guy, nor a strongman.
So, what should be done? I think we should begin to devolve control to the provinces and turn the place into a Switzerland-type regime with a weak center and strong provincial control. At the same time, the U.S. should make it clear to everyone that we are there for Al Qaeda, and Al Qaeda only. Okay, maybe we should also go after pre-2001 Taliban as well. But that's it. The key, I think, is to stop trying to dictate to the Afghans what their government should look like. When we do that, Afghans end up looking to the Taliban to fight the foreigners, and we're stuck. Like we are now.
So, I guess this is a long way of saying that we should ramp down our efforts to bolster Karzai, and instead, focus on the provinces.