Jason, I think you vastly underestimate the military-industrial complex. This is not only about US and the miliatary-industrial complex is not only about army and imperialism.
It is the whole economy, all the bureaucracy, the whole system, the whole state that is based on monopoly of violence. The violence and more than violence — just the threat of violence, cost incredible amount of energy. Besides the smaller or bigger army, it is in every state much bigger army of millions of people working in offices that use a lot of energy. Their only real purpose of living is to create an equillibrium in which the fiat money can exist. It is enforced trust in fiat. Yes it is usually mild and yes, it is still working well. But it uses incredible amounts of energy. On first sight it seems the energy would be used/wasted either way. But the truth is, that it is POSSIBLE that the energy can be saved.
We do not know yet. Bitcoin or cryptos are not money yet. POS was not tested under real attacks. We do not know how stable would be a society that is using a lot of electricity directly in POW (in cotrast to recent society that uses energy of people a la Matrix + other energy). It is still the beginning.