Except for upkeeping Bretton Woods, which you know is the accord that made US guarantee safe naval trade routes for everyone in the world.
But yeh, beyond that and perhaps upkeeping Pax Americana it is not really used or useful for anythings else.
Eventually when Pax Americana runs its course people are going to see what the US military was good for.
You should read up on events in the South China Sea.
Also pay attention to China's ever growing military and political ambitions. And the increasingly belligerent Russians.
A good chunk of that money that sloshed around over the past X years of boomtime ended up in the military, and alot more is going in yet.
Resources are getting more scarce and countries are willing to act to secure what they want/need.