My comments clearly specified that I was using a population adjusted assessment (USA 316 million, UK 64 million, a five-fold difference. Your own data supports exactly what I said. US 8 in top 10, UK 2; US 16 in top 20, UK 3; US 32 in top 50, UK 5. All as expected.
Students come from all over the world to get a PhD in the UK too. Most UK universities offer a PhD, not a DPhil (which is mainly at Oxford). Although in the UK a DPhil and PhD are the same and there is no sense in trying to pick out DPhil as you have. You can argue as you like about the extra year or two of course work in the US, or the extra year or so research in the UK. But universities in the UK and US happily hire PhD (and "lite"Oxford DPhils) from the other country, judging the specific candidate.
And from objective data on research publication output and quality, on a population adjusted basis, the UK is definitely not worse than the US.
Heck, on a population adjusted basis, the UK even gets more Olympic medals than the US!