I went to a clinic in Canada a few years ago to see a doctor. My provincial health card had expired and I didn't know. I was sick and wanted a consultation with the doctor. I said I would pay cash and was told that they are not allowed to charge people who are eligible for public healthcare. So I had to go and wait at our equivalent of the DMV (while sick and seeking medical attention) to get my health card renewed before I could see a doctor. I'm sure there are countless bureaucratic nightmare stories coming out of the US health insurance system, there will be countless more under a public system