Having a military comes out of need, not out of want.
This is really the only part I disagree with you on. (Well that and the whole "git out of the country.)
There are some in the political, business and military spheres who are so far removed from life as most people know it, that what they consider a need we wouldn't even know how to describe it. During the Kennedy Administration, the military wanted the authority to drop nukes not just on Cuba, but Laos and Vietnam as well. Clearly, none of that was a "need", because we're still here, they're still here and the world didn't see a single nuke fired in anger as a result. It's probably slightly more sanely than it was then when it was Communism vs. Us.
Having a military starts out coming from a need, but beyond that it's entirely relative to wants. And the wants of those that make the decisions and earn the money are far, far removed from the everyday lives of those they represent.
This is a pretty loose analogy, but I'll use it anyway. I know this is pretty far off, but oh well.
Imagine playing a 4X game and you want to be the most "powerful" nation by concentrating on research efforts. You want to be the most technological advanced society first and everything else is a second priority. Do you completely avoid miltary spending and production? If you do you invite some sort of invading force by those who want to steal your technology and raid your resources. If you wait until war declaration to start production you still lose because of limited opportunity costs. The war might become a losing effort before you get a chance to fight back. You can not honestly bank on any optimism that no one will attack you out of good nature if you are peaceful with everyone. There is always that "one group" who will try to take advantage of you.
As a deterrent, you would hopefully build up a military force to compete with the rest of the nations in the game or what have you. However, two nations with similar military power will fight out very long and bloody war which would probably lead to a stalemate everything being equal. To prevent long stalemates and to reduce the amount of casualties in a conflict you ideally would want to create an efficiently powerful military force to deal with conlicts and wars swiftly with minimal losses. You build up military because even if there is not an OVERT need for one right away or in the near future, it still has to exist to prevent anyone to want to mess with what you want to protect. Does the technological society WANT to build a super force to take over the world if their primary objective is to lead in reserach? No. But in essence, they must in order to prevent themseleves from being taken advantage of.
But life isn't a video game. When wants start developing over needs that is where the government and the people should speak about misuse of military funding and actions. Do I like the fact the U.S. has a base in nearly half the countires (just a guess, don't know the real number)? No, and I would probably like it even less if I was on the other side of the stick. Just because a majority of the conflicts I listed previosuly have nothing to do with the U.S whatsoever doesn't mean that a military shouldn't exist. One day the U.S. will be involved in another major war (yay...) and it's better to be prepared as one of the strongest than just the average. I can say that to any western or eastern country as well. The stronger you are, the better deterrent you have.
And my "get out of country" spiel is moreso my own frustration in regards to people who always criticize over and over what's wrong. Sure, there is plenty wrong with what the U.S. is and how they conduct any foreign policy. So as a nation I think it would be more beneficial to figure out a reasonable policy instead of just saying "let's make us weaker so people like us better and stop annying us." When you deal with trillions of dollars in any business or indusrty there will be some sort of innefficiency. If someone can find a way to cut military spending by 10% and still maintain the current military while at the same time being a leader in technological innovation then please give that man or woman a medal. What I got from the OP is that we should limit spending to make us weaker because we don't have to be "that stong" which I whole-heartily disagree with. The U.S should be as strong as they can be just like any other nation in the world.