I've always thought this, too, but recently did some research about the reason we have so many bases overseas and how it essentially keeps the peace globally and keeps the US relevant on the global stage for purposes other than media/cultural influence. In a sense, a lot of our military funding may be like paying for "preventative medicine" rather than "treatment" for an actual war - which is ultimately the most humane and probably also economic strategy. (That said, no doubt the US gov't is filthy with arms lobbyists and croney capitalist backroom deals so there is still probably quite a bit of spending we could reallocate before our empire started to crumble.)
