For an example of a country whose currency does not have reserve status and is denominated in something other(USD) than it's national currency and spends like a drunken sailor running up enormous debt till it can't be serviced look at Argentina. Once the IMF cut off credit Argentina defaulted and collapsed.
Right now we are some what similar with enormous debt but having the advantage of being the worlds reserve currency and having a very good ,albeit somewhat smaller than in previous times, military.
Once the USD looses reserve status we eventually go Argentina. So when Saddam posed a threat to the Petro dollar it was time for him to go. Saddam started to deal Oil for euros in the fall of 2000 and was being kicked out in 2003
That will sigh your death warrant every time. Follow the dots.