We could easily bomb the Taliban into extinction if our planes were allowed into Pakistan airspace.
You mean like the sterling success American drones have had?
If we just marched into Pakistan, it would be a godsend for the insurgents. Support for them among Pakistanis would skyrocket. Counter-insurgencies are very different from 'wars' - if you use conventional warfare against them, they invariably multiply. They're more like incredibly intensive policing and development operations.
Progress in getting at the taliban in the FATA needs co-operation from Pakistan. Unfortunately, the Pakistani govt at the minute is incredibly unstable and Pakistani's have other things on their minds.
Why do we volunteer more troops when other NATO countries continue to shirk their duties?
A good question, other NATO members should definitely contribute more, but be careful of thinking of NATO as nonexistant - the Canadians, for instance, have done plenty of good work.
On the other hand, though, remember that this was essentially an Anglo-American war to start with. Plenty of people feel their countries have been dragged in.