I don't think credit card debt is driving people into bankruptcy, mostly. From what I've seen (which isn't a ton, but some), people just build it up slowly buying toys and treats. Eventually they stop, either because they get smarter or just can't get any more credit, and then either sustain the debt or very slowly pay it down.

It's hard to go bankrupt from this directly because they're careful not to lend you more than you can pay back. It doesn't always work, of course, but they do a decent job of figuring that out.

Note that a lot of medical bankruptcies aren't bankruptcies due to medical bills alone, but are people with insurance who go bankrupt due to a combination of deductibles, additional non-medical expenses related to the illness, and a sudden reduction in their ability to work. Having a bunch of credit card debt instead of a bunch of savings could easily put someone in that situation, so the two probably work together a lot.

No, it's mostly just not allowing for relatively small bumps in the road. A water heater here, a transmission there, next thing you know...