While many talk of "fixing Afghanistan," the sad fact is that there was never much there that worked well or for long. It's not for nothing that Afghanistan is the poorest nation in Eurasia, and has been virtually ungoverned for centuries. What passes for a central government was established a few hundred years ago mainly to deal with foreigners (and keep them out), and occasionally help mediate tribal disputes. Afghanistan is that part of Central Asia that no one wanted, the kid that never got selected when it came time to choose up teams. Economically, there's no there there, and thus no reason to bother marching in and taking over.
For a long time, a branch of the Central Asian "Silk Road" trade route (from China to the Middle East) passed through Afghanistan. When that was the case, those parts of Afghanistan belonged to one empire or another, and Afghanistan, as we know it today, was nowhere to be seen. But larger and speedier European ships made the Silk Route a lot less lucrative by the 17th century, and interest in the area, that came to be known as Afghanistan, waned.
But American commanders in Afghanistan know that the country does have economic potential, if only communications (cell phones and roads) and order (suppression of bandits and tribal gangs out to score) can be improved. The U.S. commander in Afghanistan now wants 45,000 troops to destroy the heroin trade (which definitely does not want law and order) and suppress the banditry, so that trade and more economic activity can be established. For the last eight years, there has been thousands of kilometers of new roads built (and many more kilometers of older roads repaired). The paved roads get the most media attention, but some of the dirt or gravel roads are a matter of life and death for people in remote areas.
The Taliban see the roads as an enemy, capable of bringing in new ideas, and prosperity that will weaken Afghan will to resist all this modern evil. But at the same time, the Taliban use the roads to move around, to kill and terrorize those who don't want to live a conservative and restrictive lifestyle. But most Afghans see the roads as a means towards a better future.
Thus the American commanders in Afghanistan are also asking for more civilian economic experts. Irrigation and farming experts from the U.S. Department of Agriculture, transportation and economic experts from other departments. In most of Afghanistan, where the Taliban are not active, there has been much economic growth over the past eight years. But failure makes more compelling news, so the Taliban's efforts to halt economic growth get more attention.
To foster economic growth, you also need less corruption and more security. Stamping out the corruption will take generations, even if honest government takes hold. Right now, the heroin trade is making it very difficult to be honest. The drug gangs also prevent the police, army, or even tribal militias, from establishing security in the south. But that's what it takes to make Afghanistan inhospitable for the Taliban, and their Islamic terrorist allies.
Afghanistan is a collection of tribes and ethnic groups that mainly want to survive in a harsh environment. Nationalism is not, and never has been, a big issue out in the countryside (where most Afghans live). Prosperity is desired, but only if you have a chance to live long enough to enjoy it.