Well it wasn't exactly easy to set up the NHS in the UK either. If the political will is there it must be possible
There's a less dodgy/flippant response to this than the one I made (sorry).
The problem (and I think I agree it is a problem) is that there
isn't enough political will, and that could be the case despite public opinion being highly supportive, though I don't know if it is. Put simply, public opinion which is not well organised and is diverse and diffuse and--at the end of the day--diluted by a lot of other concerns that the non-organised public has, has to work very much harder than the very-
well-organised and
concentrated special interests of the coalitions that benefit from the present US health system, in order to overcome them and prevail in getting policies that serve the public better than insurance and pharma and the AMA.
According to a brilliant
book by political economist Mancur Olson, the efficiency-retarding accumulated influence of special interest groups grows stronger over time the more a country is at peace, democratic, settled and so on. Events that sever these networks of relationships between self-advancing coalitions and government (lost wars, revolutions, state bankruptcy, and I would include Naomi Klein's laundry list of "shock therapies" too), can sometimes restore policies that better reflect public interest not private special interests. I would classify the establishment of the NHS into this situation, though Olson does not mention it but covers many other schisms such as Germany and Japan's post WW2 economic dynamism.
So in all seriousness, I think it
is much more difficult for the US to get to UHC than it was for the UK to set up the NHS and the other welfare state institutions that it did post-1945. And that is
not because of political will
per se.
However, I don't think it can happen without torpedoing some of the financial incentives that drive politics.