the biggest issue with trying to implement the system in the US is that by itself is not sufficient.

NHs's works in other countires because they also pass legislation that regulates food/consumer products in the interest of protecting public Health.

for instance: some of the products you see in the US sold as "Food" would be deemed outright illegal to sell in these nations just from the sheer amount of sugar in them.

such regulation would in turn significantly lower the incidience of avoidable diseases like morbid obesity, Heart diseases and diabetes. this would in turn "unclog" the NHS

TLDR:implementing a NHS demands legislation that also aims ot improve the overall Health of the population. some companies would rather not have that because it would cut inot their bottom line.