The United States spends more on its military than the rest of the ENTIRE WORLD. Allow that to sink in. One country spends more on its military than the entirety of all the other countries in the world.
A lot of it is probably contractual waste, thanks to people being fucking bastards, and thinking, HEY! Free money! There's a lot of paranoia, there, too, and then there are the dominionists, who think the USA should take over the world to make way for Jesus.