But it's not like those aircraft carriers are going to show up if someone doesn't take your dollar. State backed currencies (backed by state backed armies) have failed plenty of times. History is dotted with governments who suffered by poorly managing their currencies, no matter what their military power.
Super pedantic, but I believe we have 11 active carriers and 2 under construction.
As well as the whole concept of the petrodollar.
Petro dollar is directly tied to the US military prowess. If you try to create all alternate Petro dollar they kill you. See gaddaffi for example