IMO, the best we can probably do in Afghanistan is to help them but not to dictate a solution. Perhaps our best bet is to support their exiled King as a figurehead above a general council where the different groups are all represented.

We did dictate new governments to Japan and West Germany following WWII, but those were completely defeated populations with different histories. From what I've read, I don't think Afghanistan has ever had a powerful central government (unlike Japan and Germany), so I doubt we'd be able to impose one. One risk we face is that the Afghan people would see any post Taliban government as an American puppet. Given their history and mindset, I doubt such a government would last very long.