So fight Al Quaeda. Leave the rest alone
This with us or against us crap simply isn't working. It's a police action Tom, nothing more. When Al Quaeda becomes a country then you have a case for warfare. Your desired tactics might just make that a reality since their recruiting seems to be greatly bouyed by our actions.
Oh, and by the way, the empires you speak of and their centuries-long reigns happened during times of nearly non-existant communications and they all failed miserably in the end. Also the countries they invaded didn't possess thousands of nuclear arms. Hannibal's elephants would be a bit outclassed these days.
Art