The New York patients had paid through private insurance to go to hospital and were therefore likely to be of a higher social class and healthier, whereas the NHS patients were from all social classes.The sample US hospital, Mount Sinai Hospital, is ten tiny Manhattan blocks from Harlem. I doubt the patients there are all wealthly.
We lived in London for a year and visited a friend (from a wealthy family but didn't have the private medical ins) in the hospital where he died....very poor care.
The hospital was an old WWII Quonset Hut...huge...with no walls between beds...just curtains...and the nurse visited him once a day. Sad.