(1) The United States Constitution forbids Congress (the branch that spends money) from establishing a compulsory healthcare system. It would take a Constitutional Amendment for the U.S. to adopt universal healthcare. This is no small point; it is determinative of the issue. And given the requirements for a Constitutional Amendment, it will not happen in the next 25 years, at least.
(2) Essentially all of the "developed" countries who have adopted "universal" healthcare did so before the creation of a vast medical "industry" delivering the professional and skilled services and drugs, and utilizing the incredibly expensive diagnostic and treatment tools that exist today. In the U.S., the market has spawned and mandated a vast network of for-profit, non-profit, and charitable "industries" that deliver the necessary treatments and whatnot that are required. THEREFORE, to try to CONVERT our current healthcare delivery industry to something controlled and paid for by Government would create the WORST of ALL WORLDS. Horribly expensive care delivered by government employees. Corruption and graft, fraud, waste, and abuse at previously unheard of levels. Literally, the worst of all worlds. And not to get ethnic about, the biggest thieves and exploiters would be the foreign-born doctors, as demonstrated in the Medicare and Medicaid fraud experience currently.
(3) The vast majority of Americans are satisfied with their healthcare. They get health insurance through an employer, or they are on Medicare or Medicaid, and they pretty much get all the medical care they need. The people who are "suffering" are the outliers with crappy jobs who make "too much" for one set of benefits, but "not enough" for the care they want. But these are a small minority.
Finally (4), in spite of all the criticism, the U.S. is absolutely in the top tier of healthcare delivery in the world. Most of the complaints are based on cherry-picked statistics (e.g., infant mortality, which most countries lie about), and there is no better country in which to try to survive cancer, heart disease, stroke, and so on. No better country in which to need a transplant, elective surgery, or non-emergency surgery.
Every healthcare system has its "sweet spots" and areas where it falls short. Life has inevitable tradeoffs. Is it any wonder that Leftists are the ones constantly complaining about this sort of thing? Complain about insoluble or non-existent "problems," then blame Conservatives for impeding "progress." Constant, repetitive bullshit; that's all they are good for.