Texas Ranger...
It was during the 1960's that France dramatically expanded her reach into European wide standards. This shift was tied into the EEC -- which was actually launched (1955) as the Franco-Germanic iron, steel and coal cartel.
Both nations have their heavy industry located right up close to their mutual borders. This was of major consequence during WWI and WWII.
After WWII, both nations mutually decided that it was impossible for them to ever fight again over pretty much anything -- in a world now dominated by America and Russia... particularly in iron and steel production. (Russia eventually displaced America as the world's top producer. Later it was Japan... and still later it's Red China.)
What got started as an iron cartel expanded into every manner of industrial goods production. Group Schneider (Square D) rode this wave to the top of the heap.
Paris, long ago, made electrical goods a national priority -- and designed out/ regulated out -- Westinghouse and GE product lines. Step-wise, France -- with German backing -- unified European design solutions. ( IEC )
It got off to a slow start in the 60's... and now is everywhere you breathe.
The French eventually made American imports -- de facto -- illegal. Ultimately, if a product is certified for sale in America or Canada -- then it's de-certified for sale in Europe -- and it's hangers on. (Francophone Africa, etc.)
This is the true source of grounding conductors that are green with yellow stripes. The stripe was mandated to stop the importation of cheaper American/ Canadian copper wire. It's also used to block NEMA certified equipment -- right on up through robotics.
The French argued that America's massive electrical trade allowed Westinghouse and GE to out compete European designs... that no European firm could ever push exports into the American-Canadian market.
This, in a world where Group Schnieder owns Square D outright and the largest Mexican manufacturer, too!
This gambit goes far beyond devices -- to include atomic plants. France now has the most advanced atomic technology on the planet. No-one else is even close. She'd rather export the juice than the atomic plants. At night, most of Europe is getting their juice all the way from France: Italy, Spain, Germany, Belgium, etc. are all addicted to lowest cost French atomic electricity.
When the inter-tie went down, all of Italy went dark! It took days to re-boot its grid. It finally came out that France was powering the base load of almost all of Europe that night. (!) Paris looks upon the practice as her ideal export engine. The money just keeps rolling in.
All of which is a long way of saying that America (NEMA) is, and has been, in a long smouldering trade conflict with the Europeans. (IEC) Both want to be exporters to the world -- and don't want their peer to challenge them in their home markets.
So, the devices are engineered to not quite fit each other (dimensionally) -- even if they are virtually knock-offs of each other.
We see a variation on this with the NEC mandating new technologies -- even if the stuff is not ready for prime time.
The battle is on economics... not on the engineering.
