When it comes to military spending, one must consider that China, Russia, heck everyone else does not have as large a military footprint as we do.
China's spending is more concentrated and directed , for now, regionally.
If the USA only maintained a military presence around it's own borders for the most part, you would see that number drop drastically.
Of course, there would instantly be a race to take our position if we retract. It's a competition, and the one on top, prospers most, and everyone knows it, and wants it.