Universal healthcare works just like private insurance - people regularly pay small amounts into a pool that covers the expenses of those who are currently sick, injured, or disabled. Since the number of people who are sick, injured, or disabled at one time is relatively small compared to the general population, there's frankly no issue with funding so long as enough people are paying in. So contrary to their argument, a large country like the USA will actually have a cheaper and more stable healthcare system than a smaller country like Denmark. Another thing is that people with unhealthy lifestyles are actually cheaper because they die younger - someone who say, smokes and eats themselves into a heart attack at 40 is less likely to be around long enough to rack up the medical bills that people get as they deal with the cancers and other expensive ailments that become more and more common in old age.