Again, please understand that a mechanism for exerting control over a market is not the same thing as the primary reason for exerting control over a market.
USD is in part a method to exert control over the oil industry. You are asking me to believe that if it went away, the US would throw up its arms, get rid of a substantial portion of its military, and stop trying to control the oil market. That's not a reasonable claim to make, there is no possible world where this would play out the way you're describing.
