I respectfully disagree. There are many many transactions that happen behind the scenes when you're paying with a Visa card. All transactions go through a merchant bank before ever being sent to Visa, and they may even go through a second third party. Additionally there's a number of times in which clearing and settlement occurs, both on the merchant side and on the "monthly bill" part that you discounted as irrelevant.
This all takes energy, the POS takes energy, the banks all require energy to process transactions, it takes energy to send out statements, to pay your bill. I have no clue if this entire process takes more energy than Bitcoin or not, but I can guarantee the cost of doing a transaction through Visa isn't glaringly obvious.
Far from a perfect number and you're correct it won't cover payment processors, but it's also picking up non-trivial amounts of other stuff since those data centers don't do exclusively payment processing.
But either way you wouldn't count the POS. The POS is still there consuming the same amount of power if you pay with BTC, VISA, or cash.
It's driving electrical/computational consumption efficiency but its definitely a catch-22 as with most technology.
But it should be glaringly obvious that Bitcoin is by far the most expensive way to do financial transactions. That shouldn't even be contentious. It's literally built on the idea of doing computationally-expensive busywork.
Whether or not that busywork is a waste of power or a necessary cost then depends on your social beliefs, but it's definitely going to be vastly more power-expensive than any of the existing systems.