As a fellow taxpayer, I just want to point out that another way to look at ROI on our military industrial complex is global stability safe for commerce which leads to things like being the world's reserve currency, having our debt viewed as the safest global asset class, etc. It strikes me as foolhardy to want to give this up, even if nothing lasts forever.
Edit/addition/afterthought: There are other ways to pare back military (and all special interest) spending and influence- which is a worthy effort- without abdicating a global leadership role.