I do believe there was a difference in the use of enemas between the UK and America. It was likely driven by both geography and government.
In the UK, postwar, much of the healthcare system was government run. I believe much of the mundane care was delivered by District Nurses who visited patients and triaged them and administered routine care, like enemas.. From Wiki:
"District nurses are one of the many different types of nurses who manage care within the community, rather than in a hospital or private clinic. They visit patients in their homes and provide the necessary advice and care regarding wound management, continence care, catheter care and palliative care amongst others."
The countries are vastly different in size: the UK is about 93k and the US about 3.8M square miles. What can work in a compact country fails in an enormous one. The distances are just too big. In the US one can literally live 100 miles or more from the nearest doctor or health facility.
And it's very unlikely a parent would drive 3-4 hours, just because their kid can't poo. Very different than a District Nurse who is 15 minutes away by bicycle. Hence, there is a do-it-yourself tendency in American medicine. And any mom can fill a bag then their kid.
As to equipment, there is something of a puzzle. The biggest drug store chain was, and may still be, Boots Chemists. They have been around for 150-odd years and were pretty much the sole source suppliers before the web.
They sold several kinds of enema & douche apparatus:
There was the common enameled kit like this:
https://img.techpowerup.org/181202/NmM0NTI4YmYwMThm.jpg
And a glass version, like this
https://img.techpowerup.org/181202/ZTFmNzlmMGNhYzU4.jpg
(Aside: This style seems common in the UK, France, and Germany. I would love to know who/where they were made)
Even into the 1980s, rubber fountain or combo syringes were all but unknown. I've no idea why.
Another oddity is that small volume Glycerin Syringes were apparently common in the UK from maybe the 1920s on. These syringes delivered about 15 ml of glycerine well up into a person, forcing a poo within minutes. AFAIK they never became common in the US, before the introduction of the Fleet version.