The USD is backed by military might and risk of invasion, this is known as the petrodollar it currently requires a US military that uses the equivalent resources as 140 countries.
If you consider 98 million barrels per year used by the military to protect 1.5 trillion USD, every million in the bank uses 65.5 gallons of oil per year.
You're really attributing the entirety of the US military's oil consumption strictly to the preservation of US currency? That's quite disingenuous. Did I miss the part where moving to cryptocurrency will eliminate the need for a military?
The entire economic and technology infrastructure of the world is backed up by military power. I believe we should talk about all three things: Military expenditure, energy usage, and money systems. All can be improved or made more efficient independent of the others to a substantial degree.
The things that are worth buying with bitcoins are still largely produced by the conventional economy.
If you consider 98 million barrels per year used by the military to protect 1.5 trillion USD, every million in the bank uses 65.5 gallons of oil per year.