Anyone wishing to imply that American "English" is still valid English, might like to consider this for a second: if part of an English family emigrated to America in the 1800s, then years later, their descendants flew back to England, from America, and demanded instant English citizenship, can you see how that would turn out?
"But my great great grandfather was English, so I'm entitled, and technically I'm almost English by ancestry"
Yeah? NO.
Ah, the classic rant of an uninformed British snob.
The fact that we can understand each other without difficulty already shows that we are using the
same language. We speak different dialects, but the fact that we have mutual intelligibility shows that they’re not different languages.
There once was a language called “English”, which was then carried to multiple faraway lands. In each of those
and in the mother country, this English continued to evolve, such that a) the dialects grew farther apart from each other, and b) the dialects,
including in the mother country, evolved away from the mutual ancestral form. (And indeed, historical linguists have shown that British English changed
more than American English. Both changed, but American English changed
less.)
In other words, your British English is
at minimum as far removed from the “original” English as my American English is. But the fact we are having this discussion in English means they’re both the same language, and its name is “English”.
What I find curious is how fragile the British psyche must be, given how so many Brits take
every opportunity they can to bash on American English (and American things in general).