One thing to note, I think the strength of our currency is at least partly based on the large amount of military power behind it, and the promise of stability that it brings.
Basically, it went from being backed by gold to being backed by power and promise of restraint in printing more. I guess we've largely given up on the restraint side, though.
Quite a few fallen empires have made that error of judgement. I believe it hails from a time when the military could be used to make occupied peoples pay taxes. Nowadays, a military that is much bigger than what is needed for defense suffers from diminishing returns in terms of backing the currency with a safety net.
The military is not going to force the Fed to stop printing money.
Basically, it went from being backed by gold to being backed by power and promise of restraint in printing more. I guess we've largely given up on the restraint side, though.