In what circumstance could the banking system collapse but leave the electric grid and all other infrastructure which supports the internet intact?

The internet is more resilient than that. I wouldn't want to live in a country where the banking system has collapsed, and one of the reasons is because I expect that this correlates with unreliability of the power grid; but you can run a lot of useful pieces of software on a computer powered by solar panels and batteries in the wilderness with a satellite uplink, including a bitcoin node.

Ah yes. And everyone in a country that suffers a banking collapse lives in a wilderness with solar power and a sattelite uplink.

Yes. And if a country with say 200m people suffered a banking collapse, everyone could do a Bitcoin transaction every 40 days (assuming everyone else stopped using it), and would use only about 1% of the world's electricity. Great stuff.

Venezuela?

Do Venezuelans _actually_ have much documented usage of crypto, or are they simply using foreign fiat like the USD and Euro?

One where the president prints trillions of dollars to bail out his AI cronies.

++1