What does single payer mean?
It just means one single entity (e.g. government, financed by taxes) finances health care costs. I don't think single payer federally will occur for a long time mainly because most people are selfish and myopic (i.e. "I have my employer health care so F anybody else"). I think best shot at universal health care is the existing Democratic proposal Medicare Extra for All. That way people could still keep their employer health care if they wanted to.
We already have two single payer health care systems in the US. One is the VA and we have all heard how "well" that system runs. Health care run by entrenched bureaucrats who are more concerned about job security than patient care....ugh.
The second is Medicare which is actually pretty efficient overall. It is not popular with doctors and hospitals because it severely limits the reimbursement amounts. Cry me a river.
Expanding Medicare to cover more at-risk patients is a good idea provided the price control side is maintained. Medicare should be expanded to cover anyone who wants to use it.
Continuing to prop up ACA is a mistake. It was written by and for the benefit of the health insurance industry. Premiums are increasing faster than ever. Subsidies hide these increases for most people but ultimately we all pay for it in the long run.
Using taxpayer money to mask the cost of health care through subsidies is a recipe for disaster. The student loan crisis is a good example of what can happen when the government masks costs to the consumer but doesn't control the actual amount billed.
Many countries have a two-tier health care system. A public system available to everyone and a private system available as well. I would not oppose something like that through a combination of expanded Medicaid and private insurance.
Realistically however I think that too many of our elected "representatives" on all sides of the political spectrum are corrupted by health care and insurance industry money for this to happen. Instead we will wind up with another travesty of a health care bill that ensures the continued profitability of the health care industry while sticking the public with the costs.