A Democrat can declare his support for public healthcare all day long, but actually acting on those declarations would be biting the health-insurance lobby that feeds him and jeopardize his (re)election and/or cushy, post-Congressional consulting position. It wasn't incompetence that immobilized the Democrats during their period of Congressional domination, but self-interest.
Politicians are not particularly worried about the health insurance lobby. Health care in the USA is about 18% of our GDP, which is about twice as much as EU countries with national health care. With 18% of the GDP, there are a lot of people involved in health care, very few of them in the private insurance business. There are many reasons for this, but doctors, nurses, administrators, etc make a lot more money in the USA than they do in the EU, and there are tens of millions of these people when you count everyone in the USA health care system. In additions, companies make high tech medical devices, computer systems, medical supplies, etc they sell to doctors and hospitals. Also, drug prices are not regulated in the USA (unlike almost all the rest of the world) and the big pharmaceutical companies make billions and billions of profits in the USA, and many of their employees make a lot of money.
Do you have any idea how much Big Pharma spends on Viagra, Cealis, etc commercials in the USA each year? Billions on those type drugs alone, not to mention all the other drugs they peddle. That means that the US media companies also have a huge stake in the status quo, because those billions of advertising costs go to them. You aren't go to hear even the liberal media complain about it, because their parent companies are getting all the advertising money, and they hope that if there parent companies are profitable, then maybe they won't cut back on news divisions. If you consider everyone involved, either directly or indirectly in the US health care system, health care is actually more than 20% of the USA economy.
Democrats are big supporters of Viagra and Cealis being covered by Medicare and Medicaid, just so a lot old men can get an erection even though there is nothing medically wrong with them other than just being old. The AARP (American Association of Retired Persons) lobby is probably the most powerful in the USA, and they put severe pressure on Democrats in Congress so they can get those free erections (and a lot of other non-critical medication, procedures, and medical devices). AARP traditionally endorses Democrats in most elections.
Obamacare also mandates that birth control be covered by all health insurance companies, public or private, and even insurance provided by churches to church employees, even when their particular religion forbids the use of birth control drugs. I personally have no objection to birth control, but it seems to me that churches should not be mandated to provide that coverage to their church employees if they have a religious objection to it.
Health insurance companies are a tiny piece of the cost of health care in the USA. Getting rid of them, or driving them out of business, isn't going to solve the problem. If it would solve the problem, I would be all for it, but once they go out of business the problems will still remain. Besides, most corporations are self-insured and only use the insurance companies to administer the insurance claims. That means that, unlike what most people think, it is actually the corporations that determine what is covered and what is not (except when mandated by law). But it is hard to blame corporations since even self-insured health care costs are out of control, increasing at dramatic levels each year.
Government health care insurers (Medicare and Medicaid) are even less efficient than private health insurance companies, and also the level of fraud in Medicare and Medicaid is much, much higher than for private insurance (if you don't believe me, watch the American Greed TV show in MSNBC, where a lot of the shows deal with medical fraud, mostly Medicare and Medicaid).