I agree with Perv, the terrain is forbidding, and although the US has better technology and more firepower, the environment works against these advantages. Additionally, given the territorial disputes between Pakistan, India and China, sending soldiers into the disputed areas where OBL is presumed to be hiding would antagonize several countries who could all claim to have been invaded and would each have to react more forcefully than the next to maintain their claim.
Yet the status quo sure isn't very satisfactory, it can't be that if OBL hides in this location he will be 'safe' and it sure doesn't seem like Pakistan can get him out. The US ought to work with the Pakistanis to get OBL. Reach an agreement to train the Pakistanis with the improved technology and firepower, allow some specially trained US forces to go along and work out an arrangement so that they can coordinate the effort.