I misspoke. It is not built around military SPENDING specifically. It is built around the military, and the preferred access to resources that our military provides.
We have the largest military in the world, and military bases in more countries than any other nation on earth. We also have the largest and most powerful navy, and with it the implicit control of the seas.
All of that military power assures that foreign countries need to hold US dollars. Specifically the petro dollar underpins our economy. Just look at whatever happens when the leader of another country tries to stop selling oil in dollars.
To understand how the military supports the economy, you have to stop thinking in paper currency and look at resources. Look at how many resources are being dedicated to maintaining a military footprint around the world, and how many resources are not being allocated to maintain basic infrastructure at home.
It has been almost a century since Smedley Butler declared that "war is a racket" and not much has changed since then.
Only instead of bananas and sugar in the Caribbean, it is uranium and lithium in Afghanistan