English has always been gloriously open source, and anyone can fork it. It is not owned by anyone and words mean exactly what you intend them to mean, and no-one can tell you otherwise. And you can spell or pronounce words just how you like, despite what they told you at school.

That said, your social group may set its own expectations, and you may want to fall in line, say in your job application.

So if what you speak is based on English, it's English (in my opinion - and by the way I am English).

Oh, and Shakespeare would have spoken with an accent more like an American than I do. But don't tell film makers, our actors need the work.

It really depends on where you are, I think in Europe the English taught at school and considered the regular one is British English, but if you take movies/series/music, the broader one is US English.

Considering that the English-language web is almost completely occupied by USians, it would be hilarious if they were required to finally declare that they speak ‘American’ and not ‘English’.

Not at all. It usually means that the person writing that assumes it's a common thing globally.

UK English being "proper" hasn't been a thing for decades now. Compare news reports in former British colonies from the 60s to now and you can literally hear the change in attitude toward's the "Queen's English".

No.