It was one politician who blocked a full national health service back in the 70s despite bipartisan support for it - IIRC he used his position as ranking member

It was one politician who blocked a full national health service back in the 70s despite bipartisan support for it - IIRC he used his position as ranking member on the Ways & Means committee to stonewall the whole thing. American political parties are probably some of the weakest in the world, they have almost zero ability to control what their members do or even who their members are.