In an otherwise good article on why the United States does not have a single payer health care system, and why it might be a good thing there is this paragraph:
There’s only one catch. Most Americans just don’t believe it can be done. The health care crisis may turn out to be more of a problem of ideology than economics.
Much of the resistance to a single-payer system appears to stem from a lack of confidence in the nation’s ability to make positive change ... Changing the minds of so many millions of people isn’t done overnight. But sooner or later, persuading people to do something that’s in their own economic interest ought to succeed.
The major stumbling block to reforming health care in the United States is that there are two large groups with a huge vested interest in aspects of the current system: insurance companies and physicians. For better or worse there are a lot of people employed by insurance companies in administrative, management, marketing etc ... roles who quite understandably like their current job, are well paid for it, and don't want the government and the public to combine to up end their life.
Another reason health care costs and expenditures are high in the United States is that, relative to other professional groups, physicians are very well paid. Now, some of my best friends are doctors ... so it is impolitic of me to suggest too strongly that they are earning too much, but on average they are. No doubt most of them do a fine job for the money, but it does contribute to how much Americans pay to live, on average, shorter lives than in most Western countries. Perhaps Americans live well enough in their slightly shorter lives that they still come out ahead all things considered. Perhaps.
In any case, the point remains, there are people who do very well by the current system. They would be silly to want to change it too much. Not unreasonably they use the American political system and media to sow enough confusion about the benefits of a big change in health care funding that the public appears to lack confidence in the change, at the same time as they lack confidence in the current system. Hence the continued piecemeal reforms to American health care. The people who know that, in the long term, a single payer health care system would be better (on average) for Americans are economists and academics, and have neither a large financial incentive to change the system, nor the organized politics and media resources to counter the voices of insurance companies and physicians.