An article in medscape points out that we already have national health insurance:
Could national health insurance fly in the United States? The truth is that we already have it. We call it Medicare, and it is not so different from publicly financed, privately delivered healthcare available elsewhere. Americans like Medicare. As for their doctors, hands-down they prefer Medicare to private insurers. Because Medicare doesn’t have to generate profits, or spend millions on advertising and Washington lobbyists, it can offer more coverage for less.
The article points out that health care coverage now approaches $11,000 annually per family and that burden is falling onto the family and no longer completely on employers.