Empires in decline have been known to debase their currency in order to finance their overreach.
And how would a gold standard change that?
Rome did it without fiat currency.
As I said before, many of the people who want a gold standard think it will fix every problem we have.... when monetary issues/policy are the LAST thing that anyone should be concerned about politically.*
*That is, given the amazing stability and restraint we've seen for almost 40 years. We've got a good monetary system. Our money problems are all related to spending.