Other countries are not the United States. Half our population basically pays no federal income taxes while at the same time complaining that they are overtaxed and the rich don't pay enough. You think those people are going to agree to fork over the muhla for a single payer system?
Truth be, we already pay enough in taxes for a well-thought out healthcare system. That is what is so maddening about the American system. We pay in twice as much per capita as the rest of the first world but get back half the quality. Single payer would cost us LESS in the long run, but the political consequences of it are unfathomable. That is why nobody will do it. Wasting billions of dollars a year is politically preferable than hanging your own party with a run at single payer.
Again, health care is the ultimate political football. Single payer pretty much takes that out of everyone's hands once and for all. If the Republicans were in power and proposed it, they would be fought tooth and nail by the Democrats, labor, the health care industry and the insurance industry.
Despair.com once had a poster that said something like, "If you can't be part of the solution, then you can be paid to be part of the problem." That's the American healthcare system in a single sentence. Everyone knows how it could be fixed, but the capital in allowing it to stay broken is too great to ignore.
Imagine if tomorrow everyone woke up agreeing on abortion or gun control? What a political disaster that would be for both parties! Extreme wedge issues get people to the polls and keep the party coffers full. A 'win' in healthcare, on any level, by the Democrats is a catastrophe for the Republicans. It would be no different if the parties were reversed.