The US's problem seems to be that citizens demand a very high level of (costly) medical care, which would not be sustainable if implemented as a taxpayer-funded universal program. As an example, the numbers which I've seen indicate that the USA has about 10x as many MRI machines per capita than Canada (which is generally a comparable country). The other big problem is the way that Medicaid is implemented, with funding and accountability divided between the Federal Government (which doesn't have the constitutional authority to run healthcare), and the States (which do); this is rather similar to Canada, which also has major issues caused by this division.