To add to what has already been said, the changeover was part of a movement in the early 1970's to establish ISO standards for bicycles. Fred DeLong who wrote for Bicycling chronicled the process at the time. If I remember correctly, English steerer tube (25.4 o.d .and 22.2 i.d. aka 1 inch and 7/8ths), bottom bracket (1.37 x 24 tpi) and freewheel threading won out (1.37 x 24 tpi), in part because there were also the Japanese standards. The only standard that didn't fully stick was the stem pinch bolt standard of 25.4. The industry standard for road bars stuck with the Italian 26.0 until recently, although 25.4 is standard for mountain bars and a lot of Nitto stuff.
This process made the French, Italian, and Swiss standards obsolete.
I believe that Cyclo Benelux made freewheels in both French and English threading. My first multi speed bike in 1969 was a Dawes with 26x 1 1/4 wheels *which my best friends oldest brother had bought in England in the very early 1960's. It had 5 speeds , wingnuts and a Huret Alvit derailleur. When I got it, I was given all the catalogs (now no where to be found) which showed all sorts of neat bits and pieces- Bluemels fenders, all rounder and north road handlebars, in addition to Maes bend, single speed flip flop wheels, three, four and five speed freewheels and I specifically recall Cyclo-Benelux as a freewheel maker.
Somewhere in the cobwebs there is a replacement.
*After a year of riding the tires blew out with the casing splitting. My mother and the neighbors came running believing it was a gunshot. The tires could not be obtained in the area, if at all in the US at the time, nothwithstanding that the local bike shop was Klarsfeld's in Albany, a renowned ancient establishment with a display case of vintage stuff on display today. To ride again I had to learn how to build a wheel. two new 26 x 1 3/8 rims, the old spokes, a screwdriver, three days and a file to hand file all of the protruding spoke heads down below the top of the nipples. Then the head lug cracked and it had to be brazed. The bike continued to be ridden, and was sold back to my best friend's younger sister who rode it until at least 1975.