Why can't we have healthcare systems like Norway, Denmark, New Zealand, etc? They offer better (government) healthcare and life expectancy is higher than the U.S.
Part of the answer is geopolitical history: Of all the major participants, the USA suffered the least from World War I and World War II. That's what it comes down to. (New Zealand was part of the British Empire during these wars, so its policies are inherited from the experience of the UK, proper.) WWI + WWII left the major participants thoroughly devastated, with a large number of young men coming back from war and no economy to speak of to take up the huge labor influx. Most of these countries had two choices: Adopt a Bismarckian approach or face dictatorship. (The USSR simply continued dictatorship--everyone loves your policies when the alternative is the gulag.) The Allies were painfully aware of the economic and social problems that made the Nazis and Fascists so popular, and every Allied country had a pro-Nazi/pro-Fascist movement before WWII.
So, that was their apparent choice: Follow the Weimar Republic into destruction and start the cycle over again or adopt at least some level of paternalistic government. Under DeGaulle, it was conservative paternalism. In the UK, it was Labour-led social programs. The Social Democrats did it in Germany. In the USA, on the other hand, the economy took off like a rocket. We had the ONLY large industrial base that hadn't been bombed to pieces. It was easy to pay for healthcare through private means.
Part of the answer is racial: It has been well established that it is far easier to implement paternalistic systems, like "national healthcare" in racially homogeneous countries. It is no surprise at all that Scandanavia leads the way in this, since it has some of the least racially diverse countries in the world. However, as racial (and other ethnic) diversity increases, it becomes harder to obtain agreement to widespread social programs. People are innately inclined to accept programs that help "their own kind". Being happy to help others requires a higher level of refinement. The explosion of diversity in immigration after WWII made matters even more difficult in the USA.
Part of the answer is economic history: The USA was a pioneer in the insurance industry. Our government didn't have to worry as much about this issue because private benevolent aid and insurance companies were chugging along nicely. After WWII (funny how that keeps coming up), economic entrenchment of an insurance "industry" was massive, specifically because employers begged Roosevelt to allow them some way to compete for labor even in the face of a wage freeze. It was illegal to offer higher wages due to "wartime measures". Thus, how could you attract workers? Remember, you couldn't offer less hours and same total pay, since that would raise the hourly wage. So, the us government worked out a deal. They would exempt the portion of health insurance premiums paid by employers from taxation. This would allow employers to carry a larger portion of the insurance burden. Health insurance revenues skyrocketed, and a very powerful industry and lobby was born. Any attempt to impose a national system would have to fight against this industry.
Part of the answer is propagandic: From 1947 to roughly 1960, the USA defined itself as the world's sole defense against "Godless Communism". This is the era in which the Pledge of Allegiance was propagandistically altered to include "under God". This is the era in which the national motto was officially changed from "E pluribus unum" to the propaganda phrase "In God we trust." Thus, since anything that smacked of "communism" was automatically "Godless", and since the USA was the self-appointed defender of God (He's so helpless, don't you know) against "communism", and since "communist" propaganda heavily stressed how the state should supply services to the people, active political hostility built up in the USA against such programs.