> Actually, I would've have assumed the other way - that the NHS was better than the US system.

I thought it was relatively uncontroversial that the major problem with US healthcare is not quality but cost. And the UK NHS is widely regarded as one of the lower quality implementations of single payer in any modern social democracy [0].

[0] https://www.usnews.com/news/best-countries/rankings/health (#23, but Canada is actually worse!)