The notion of rights as inherent in human nature is a philosophical concept. Rights in law, individual rights enshrined in the laws of this or that land, is a very different conception of the same word.

The question whether healthcare is construed as a philosophic right depends on the philosophy adopted. Adopt as one's core philosophy the tenets of laissez faire capitalism, and one might conclude no such right exists. Adopt as one's core philosophy the tenets of Christianity, and depending on your version of Christianity, the notion that healthcare as a right can be derived without great effort from the golden rule.

In the current context, the question properly put is whether Americans ought to adopt healthcare as a legal right? If they answer in the affirmative, and if they elect lawmakers who actualize that affirmation in law, then ipso fact healthcare becomes a right in the US; just as it is in virtually all other first world countries. 

American's decide if it is a legal right.