You can't say how efficient it is without calculating how layer 2 scaling affects per transaction energy usage. You can do millions of layer 2 transactions that eventually settle as 1 transaction on the main chain.
You would have to do literally millions per on chain transaction using bitcoin to match ACH, visa or a proof of stake chain.
This is of course after you consider opening a single LN channel for every human on earth would take 75 years and 300 billion dollars if the chain did nothing else. Like putting in a request for a Soviet phone line. LN has quadratic routing efficiency and is boat anchored to garbage.