I'm a Brit, living in America. Today, I was just beginning to gather the documents for my 2017 tax return (I file my return very early in the following New Year, for various reasons). The medical expenses for my wife and I so far this year amount to at least $24,000. About two-thirds of that is the monthly premium for insurance, the remaining third is "copays" and "deductibles" not covered by insurance. We buy our own insurance because we are self-employed.
We are both about 60 years old. We are not particularly sick, and my diabetes was a minimal part of the cost, given that I am T2D, do not take drugs or insulin, and do not self-test. We simply had a few random "medical episodes" such as me having kidney stones, and various aches and pains that needed X-rays, physical therapy or other treatment. We also both had full annual medicals, routine colonoscopies and other preventive care. Not to mention eye care. Also dental care, for which we do not have insurance (dental insurance makes little sense for individuals in the U.S.; those who have it are either on government programs or get it through their employer).
Our general health insurance, by American standards, is excellent and we can afford the high premiums (we make too much money to get any subsidy from Obamacare). The actual cost of our treatment this year was a fairly large multiple of what we were actually charged, after the insurance payments kicked in (we actually get to see the "before" and "after" billing statements and they are fairly mind-blowing).
The U.S. system is deeply broken. In practice everyone does get treated -- you will hear very few stories of people who won't get accepted for treatment at one emergency room or another. The costs of treating all those un-insured people is borne by (1) those who do have insurance, and (2) the taxpayer. Millions of un-insured or under-insured people skip their preventive care. Obamacare was a brave attempt to fix the problems and in fact made a big difference, but the real problem is a lack of recognition here that medical care is a fundamental human right. Also, a fairly widespread attitude that people are somehow to blame for their own bad health.