Yes, it is unconstitutional to have a national health care law, because there is nothing in the constitution that allows the Congress to compel people to buy a certain financial product just for the reason that they exist in the United States. The commerce clause does not allow them to compel commerce, only to regulate it.
Is it unconstitutional for us all to be told that when and if we own and drive a car we must purchase a certain level of automobile liability insurance? Of course not, even if it were said on the federal level. So that means there is nothing unconstitutional about being required to have health care, especially when the subsidies exist.
When it comes to the United States of America along with other countries across the world we must look at the actual law and what is inside the law when we discuss the issue at hand. Certain things within the law may not be constitutional such as some type of mandate among other things.
I do not believe it is unconstitutional to have a national health care law. As a low-wage worker I've never been in more despair than I was when I had people look me in the eye and declare I don't deserve medical care. I've done what I could but the world has offered me zero upward mobility. I find it terrible that some people find my input into society as valueless. I hate our capitalist society.