Why oh why is there such a difference between JAA and FAA?
I don't think there's a polite answer to that.
It the same as the answer to "why does my phone work in 199 countries in the world but not the USA", "why are paper sizes the same in 199 countries but not in the USA", "why do the USA use T1 lines where everyone else uses E1" ect ect ect ect ect ad nauseam.
The charitable interpretation is that the Americans are worse at NIH than the rest of the world. The even less polite interpretation is that they regard any "international standard" as being "European" and therefore by definition "communist" so they won't have anything to do with it.