I think it's actually less significant for the dollar to be a the defacto reserve currency than it is to be the defacto exchange currency. Trillions of dollars

I think it's actually less significant for the dollar to be a the defacto reserve currency than it is to be the defacto exchange currency. Trillions of dollars change hands every day on currency exchange markets alone...several times more than the second largest currency. This is due to the status as the exchange currency, or the most common quote currency for trading pairs. This effectively means that if a Libyan importer in Tripoli wants to buy Honduran frog legs, there is going to be one exchange from Dinar to USD, and one exchange from USD to Lempira. For this reason, global trade both depends on and is fueled by the liquidity provided by the dollar. This relationship of liquidity with the dollar is what creates the petrodollar. People and governments hoard dollars not because of its use as a means to buy oil, but because of its use to buy literally anything that is not sold in their home currency. Financial assets for hoarding can easily be replaced by other hoardable financial assets. Liquidity, on the other hand, can not.