The French didn't like it when the Lingua Franca switched from French to English and the Brits still whine that British English is no longer the dominant variety.

It's a trade-off: you can write in your regional dialect or you can write in a more widely understood global style.

It's not really comparable, almost every native English speaker can understand most British English fine, it's only when people use excessive slang or regional accents that people have issues (and that's an issue with any language - it can easily be an issue among native speakers within the UK!).

It doesn't really matter if you natively speak British English instead of American English, whereas French and English are obviously completely different languages and the switch made French a lot less useful and English a lot more useful

Lingua Franca, an Italian phrase, referred to a form of Spanish.

Or more generally: either everyone uses it or it stays the same.

Nobody speaks the One True English. That is its power.