Its single provider when veterans use VA hospitals, where the physicians and administration are on the government payroll. But for retired vets on Tricare (or its equivalent) it operates more like single payer, where the insured can use any in-network hospital. Its a little bit of both, depending on which benefits the patient is using and how he uses them.

From what I've read, most of VA's systemic issues stem from being a single provider. The abuses and horror stories took place at VA hospitals where the administration was inept at best, and corrupt at worst. I think VA stands as a stern counterpoint to those who think single provider is a feasible solution. Krugman is, for neither the first nor the last time, the spokesperson for this particularly faulty line of thinking. http://www.nytimes.com/2011/11/14/opinion/krugman-vouchers-for-veterans-and-other-bad-ideas.html?_r=1

On the other hand, Vets and their families who are on Tricare can go to in-network hospitals outside of VA hospitals. There's still eligibility requirements and co-insurance and co-pays, but the government as a single payer foots a lot of the bill for premiums, which don't increase at rates similar to what we've seen Obamacare plans rise. Part of the lack of rate increases is due to eligibility requirements, but mostly its due to the relative bargaining power of the Federal government. This is true for Federal employees by and large, as well as for employees of large corporations. These employees benefit not only because their employer pays a substantial portion of the premiums, but because the premiums themselves are negotiated to be lower, largely because of the scale and bargaining power of the employer who negotiates directly with the insurer. If that sort of bargaining power existed for all citizens, I don't know that it would be such a terrible thing.

Single payer definitely has its issues, so its not some magic cure-all. But I think having a single-payer option could be a viable option.