Thats because the American went off on their adventure in Iraq… Also, besides the fact that the Taliban have only regained some steam after a number of years following their defeat in Afghanistan, the US cant fight terrorists hiding in FATA… Hence the need to train Pakistani forces to do the job.
Otherwise, the US has been pretty succesful in its anti insurgency efforsts. The Surge in Iraq obviously worked (as much as I hate to admit it), and the drone attacks within Pak have killed some really big name terrorists.