All this money isn't being thrown into a burn pile.
It pays American soldier salaries, it buys products from American defense contractors that provide hundreds of thousands of jobs, it funds R&D that trickles down to the rest of society.
Thats more than 1 million soldier salaries and probably hundreds of thousands of jobs with companies like Boeing, Raytheon, etc.
And I know this is a generalization, and that some of our sharpest minds and highest caliber people are in the military. But I also have quite a few aquantences that really seemed to be on a bad path until they joined the military. It adds discipline and provides an outlet for agression as well as a salary for some people who would otherwise be difficult to employ. I would hazard a guess that without the military, domestic crime would go up a fair amount.
Again, this is not an endorsement of the military industrial complex, but I think that many tend to think of government waste as just total waste. When in reality, it's just a really inefficient engine of wealth distribution.