I am grappling with this but I can't.
You did not know that large parts of the world default to 12h time?
This is absolutely NOT an American thing. I am not American and have never lived there. I am 58 years old, British and Irish, and lived a decade in Nigeria and a decade in Czechia. I have travelled widely around Europe and can get by in 6 foreign languages.
12h time in real daily life is more common everywhere I have ever been. Only minor subsections of humanity -- military people, maybe -- work on the 24h clock.
I am 38 and British and use 24hr clocks exclusively. This is also very common on the continent - the French nearly always use 24hr time for everything
In the operating room, all the wall clocks are 12 hours but all records kept by humans are 24 hour time.