Comparing Visa transactions to Bitcoin transactions is definitely comparing apples to oranges.
A Bitcoin transaction on the blockchain is layer 1. A visa transaction is layer 3 or 4?
Lightning network is layer 2 and you could have >700,000 transactions in a lightning channel before settling on chain, so there you go Bitcoin layer 2 is more energy efficient than the common financial system layer 4.
That's a political opinion. But regardless of its validity, I'm not convinced that this justifies a single Bitcoin transaction producing as much CO2 as 700,000 Visa transactions.