The statement, "The US spends ~$14,570 per person on healthcare. Japan spends ~$5,790" is about the average amount that the country as a whole is spending per person on healthcare, not what any given individual is paying. Per-capita GDP (i.e. the average economic output per person) is the most relevant comparison.
To some extent it's circular: the US has a higher number of GDP because it spends more on healthcare. The broken leg version of the broken window fallacy.
https://data.worldbank.org/indicator/SH.XPD.CHEX.GD.ZS?locat...
So the USA is still significantly more expensive as a portion of actual income. “GDP per capita” is a relatively useless figure