like I said, your implications are vague and non-specific... I've given you 2 pointed examples (Canada & Germany) that more correctly describe, per your phrase "some form of", 2-tier within these respective countries. And so all you do is peal off a non-specific country list that does... does... what?
That allows people to pay for services if they don't want to wait in a queue. Right now those people are going to other countries for such services. What kind of model is that?
I'm suggesting that a 2-tier system shouldn't be this third rail. Allowing people, who can, to pay for Healthcare is not some avenue down a US model.