I did not study closer the NHS because, in its concept, it is similar to what I experienced back in my native Poland. A few occasional reports here and there confirmed my expectations.
In many comparisons, NHS appears cheaper and easier to navigate for patients. We cannot even say that the American system is more convoluted because there is no system. It is chaos. You may look at the review of both systems here: https://www.manhattan-institute.org/html/american-healthcare-and-nhs-10979.html.

For example, they claim that the mortality rates in cases like stroke or heart attack are much higher in the U.K. than in the U.S.