I always go back to the Constitution. What contract did I tacitly sign? It says, "promote the general welfare". The Founders did not define what they meant, but certainly we can use common sense to derive some reasonable conclusion as to what they envisioned.
Does the highway system, starting with the National Highway in 1814, promote the general welfare? Yep on many levels. So the question should not be what is viable or not but what do Americans expect from their government? If the majority expect nothing but a highway system, then so be it, but I suspect when the electorate is apprised of the many ways government can assist them i.e. promoting the general welfare, then they would be more attentive to a variety of plans.
Once the electorate knows what it wants, then we can talk about how we pay for it. I think it is clear SS and Medicare promote the general welfare. Would it be such a large leap to expand coverage for all citizens?
As you say, NWP, many countries have universal coverage and Germany has had it since 1888 and they have a variety of systems to ensure their citizens have coverage. The people making claims we can't afford it or that it is unAmerican are misinformed or disingenuous.
Have the debate!
aside:: should government not fulfill its obligation, I believe the Constitution tacitly implies the contract is null and void and should be dissolved.
ignorance is the enemy without equality there is no liberty