Single payer has some flaws, but it might be superior and is worth the discussion. As long as premiums are deductible and hospitals get tax breaks based on public service or religious affiliation government is deeply embedded in healthcare already.
Right now healthcare is provided by medicare, the VA, private insurers and public insurers.
Medicare is single payer and although not perfect operates as pretty much the lowest cost in terms of prices they've negotiated. The VA has really mixed and some awful reviews, but apparently not for lack of spending and many vets are now being allowed to opt into the medicare system. So the argument there is the money is not well spent. This is probably the biggest argument for the problems with a single payer. Some VA facilities are great, but many are shit. So fix the shit facilities - not an overnight process and it will take time, but they need to be fixed irrelevant of who pays.
Private insurers - generally paid by corporate premiums which are tax deductible to the employer. They are also capped at 20% retention and their profits are taxable. So they are living with a government subsidy and the taxes they pay go to the government and end subsidizing medicare in the end. So what happens if you close them? People at the firms lose jobs and that is a problem, but you also lose some of the cost. Stockholders become disenfranchised and you can't just convert the property. Many private insurers are also providers - they own hospitals and other facilities. So value their assets and buy out their insurance assets and leave their provider assets.
Mutual insurance companies like many of the Blue Cross providers and religious affiliated facilities, again a government subsidy through their structure.
Medicaid and the uninsured. Basically the poor and the uninsured and I think this is point Buffet was driving at. In a country with this much wealth we should find a way to cover everyone.
Some states expanded Medicaid under the ACA and 18 didn't - this was simply politics and is clearly part of the problem.
Are their countries that have single payer and do it well. Sure and their are countries that have single payer and do it badly also true. Steal shamelessly from the countries that do it well.
Doctors are well paid in the US -
Hospitals have very low ROI and they are consolidating in an effort to get economies of scale, but it is a nonsense model under the current system.
In the Chicago market - where I live - two of the best hospitals in the area aren't in the system of many private insurers - they are in Medicare and provide millions in benefits to Medicaid and the uninsured. This is nonsense.
The EU provides healthcare to all of it's residents no matter where, inside the EU, they travel.
Healthcare is almost 20% of our GDP which almost twice what most countries with single payer spend.
Single payer doesn't mean free, but it's a crime that at almost 20% of GDP we have millions uninsured.