I've become more staunchly single payer after I had my first major medical hurdle of my adult life this year. I had switched insurance in January, but apparently my old insurance had a bug in their system. The effect was that they were accepting my claims, but then denying them. So I had to coordinate both insurances and get them on the same page. Then I had to call every one of my many providers, get them to understand, and then get them to reprocess the claim on their end. It was miserable and I had to deal with it while I was still dealing with a broken wrist and just hoping everything would work out.
I feel awful for anyone who has to deal with that and has less time than me. I had to take notes during every phone call and get the numbers of customer reps so they could vouch for what I was saying