If you mean PPP, then the reason is simple. How much a janitor is paid to clean a research lab's washroom doesn't materially affect the quality of the research produced. There are other measures that look at things like papers cited or page rank like algorithms, and on those USA does even worse if I recall correctly.
At the end of the day, though, this is a distraction from the core argument. A valid defence of US healthcare policy is not "but we're good at research." Imagine if China was trying to defend their overbudget and under-effective military by talking up how much they've done for global aeronautical research.
Grandma lost her house because she got kidney stones, but, butterfingers, at least we research stuff! Oh and often times our pharma kills more people than it saves and true justice is never metered out ala opioid epidemic.
