Thanks for this interesting observation. I am not sure whether it is true that there are more ostomies in the UK, or whether there are more UK residents per capita willing to be active on these sites.
I tried to find some statistics on this issue but they seem to be in short supply. However, my investigations did enlighten me about a couple of things regarding the numbers of physicians and what they are engaged in. (see: https://www.healthsystemtracker.org/chart-collection/u-s-health-care-resources-compare-countries/#item-practicing-physicians-density-per-1000-population-2018 ).
It appears that the USA have fewer physicians per capita - but there are many more 'specialists' (earning as much money as they can!).
Taking just these two items of information and overlaying it with social dynamics, and the natural tendency of these professionals wanting to gain social recognition and prestige. Then we might presume that not many of these 'specialists' would percieve stomas as a prestigeous area to work in.
One might 'guess' that with a National Health Service, based on the more altruistic principles of treating everyone and anyone who has a problem, whether they can afford the treatment or not, there may be a concommitant social recognition and appropriate prestige accorded to those physicians who choose to enter aspects of the profession that might be deemed as less 'desirable' (especially as a conversational gambit around the dinner table with guests they might want to impress).
Of course! it might be down to something as simple as 'what is in the water', but it's good to speculate on differing perspectives on these issues.