Cave nukes will be the ONLY solution, shy of expending our Special Forces lives!
Afghan terrain is well suited to tunnel complexes superior to the clay-laterite we encountered in Viet Nam. These were put in place with industrial means, as opposed to manual labor, too.
I'm not a defeatist, I want them to use ground penetrator nukes and do this right, not spill a bunch of our blood rooting them out. We have way too much more that needs to be taken care of elsewhere. We can't be sucked into a long, bloody drawn-out battle of tunnel warfare that kills a bunch of our Special Forces! It would be foolish to expend their lives, when we have the nukes required at our disposal.
On a good note, the ground would contain the blast, making really small yeilds extremely effective. Most of the fallout will stay in the ground, too!