The monstrous energy usage comes from trying to brute force a single hash. It is entirely decoupled from transaction volume.
Fixed costs are amortized. The block's footprint is spread across transactions. Arguing otherwise is like someone taking the power bill of a bank to infer the cost per teller-window transaction, and the manager arguing that teller-window transactions don't burn energy, branches do. Yes, sure. But also irrelevant.
And yes, if the branch tripled in size its energy use would reduce the per-teller energy footprint. (Assuming constant transaction volume.) But that's a hypothetical.
Sure, if you're more interested in talking points then useful metrics. Increasing or decreasing the block size limit would lower or increase the "cost of a transaction" (since blocks are generated on a schedule commensurate with difficulty, which is roughly a function of how many miners there are) without actually changing the amount of power consumed.
What you're doing is basically correlating the world's average temperature versus the number of pirates and declaring that pirates are responsible for global warming. In reality, the two variables are unrelated and not even correlated.
Assuming constant transaction volume and other factors related to difficulty. You have a point. But it's far from a panacea for proof of work, and certainly not at the threshold to derail coming taxes and regulation. (Though one might find a way to structure the taxes such that they reward a productive increase in the block size.)
Of course they’re related. It’s trivial.