Earlier quoted context omitted.
> that are similarly culturally homogenous London is culturally diverse. Moreso than any US city. And its NHS seems to be working ok.
The NHS doesn't exist only in London. It covers the UK, which is 87% white (followed by Asians at 7%). A nationwide system in the US would be covering far larger and more diverse areas.
It's incorrect to say that the English NHS is a monolithic thing. It isn't.
The NHS is regional. It's split into regions by "clinical commissioning groups". There are 32 CCGs in London. These are independent from each other, and from the rest of the UK.
http://officelondonccgs.org.uk/what-is-clinical-commissionin...
> Clinical Commissioning Groups (CCGs) were created following the Health and Social Care Act (2012), replacing Primary Care Trusts on 1 April 2013. They are clinically-led statutory NHS bodies responsible for planning and commissioning health care services in their local area. There are currently 207 CCGs in England.