There are some serious constraints that I think would have to be considered by anyone trying to design a national health care package:
1) It cannot provide less, or less rapid, coverage than the typical American policy does now.
You don't even have to go past number 1. It's a show-stopper. As we just saw, and as I have pointed out many times, the component of our health care finance system that is in the worst shape is the component that is publicly funded. Maintaining the current level of availability of health care services under Medicare is not going to happen. Maintaining it under "Medicare for all" is not going to happen, squared.
If politicians thought that they could take over the health care system without making huge cutbacks in availability of services, we would already have a single-payer system in Woodstock-nation states like Massachusetts or Oregon. Single-payer in the United States is a chimera, like energy independence. Single-payer's political appeal here could never survive a serious attempt at implementation.