While I agree with much of the content in your post, I think you're discounting the very real and tangible effect of letting your dogs off the chain every once in awhile as a reminder to those who would seek to harm us, that retribution will be swift and excessive. You kill 3000 of ours, we spend 10+ years killing between 1.3 - 4 million of yours and anyone else that lives in your vicinity. While it may not deter the maniacal zealots (nothing will short of death will), it does send a very clear message to the rest of the world. Something along the lines of you mess with the bull, you get the horns.
We may disagree on much about the war on terror, but I would strongly disagree that the show of excessive and frightening force abroad doesn't contribute to the defense of our own soil.
In general we live in a civil society, and every once and a while some jackass comes along ruins the party and sticks his dick in the mashed potatoes. That party pooper right now are the radical Muslims highly regarded in the Islamic state; where ever they may be. With the birth of ISIS I would actually tend to agree with you, that our military presence should be stronger now than ever before. If we had this discussion 3 years ago, I'd completely disagree.
I take it you've never read the book, "The Art of War" -- having done so, you'd know Sun Tzu would highly disapprove of the United States military actions.
"The supreme art of war is to subdue the enemy without fighting."
"Know your enemy and know yourself and you can fight a hundred battles without disaster."
"Know thy self, know thy enemy, a thousand battles, a thousand victories."
It's no coincidence many successful war time officers read this book, along with some of the most successful executives around the world.
Hot tempers never get people anywhere good.