Too bad Walmart greeter isn't making "per capita GDP".

The Walmart greeter also isn't paying for the bulk of their healthcare expenses because Walmart provides subsidized health insurance to all employees who work at least 30 hours per week. All US employers with at least 50 employees are required to do so under the ACA. If the greeter worked fewer than 30 hr/wk, they wouldn't get insurance through Walmart, but they would likely qualify for an ACA subsidy that covered close to the entire cost of a health insurance plan on the marketplace.

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.

Some quick googling suggested cashiers at Seiyu in Japan earn $7-9/hour USD while Walmart is about double that.

If the Japanese cashier makes half the amount, but spends only 1/3 on healthcare that still seems to favor Japan

Well sure, then you're kinda cherry picking data that could easily be considered within a margin of error to make a rather unconvincing point

It is not cherry picking to respond to presented data

It's cherry picking to describe the typical worker experience? You do realize that vast majority of Americans don't make more than $100k right?

Whats your point, US healthcare is ridiculously expensive to detriment of all US citizens sans those working for health insurance conglomerates. Any objective data you pick will show this, no need for strawmen.

It’s really good for clinicians and their paychecks, too.

They make more than they would in Japan. But people can make $0 in any country. Regardless, part-time Walmart greeters are fortunately not paying full price for health insurance in the US.

put another way, they're so poor that the US gov has to subsidize their healthcare since they couldn't get insurance or care otherwise.

I'm curious what you're implying. Is there a country where the poorest person is so rich they can get all the insurance and care they require without government subsidy?