Dunno what the "Kings (H)English" might actually be...I do know though that I've never spoken it and nor I suspect have the majority of English speakers in the UK conversed in whatever the contemporary idea of "Kings/Queens English" was or is.
Theres lots of poor English about certainly but I suspect Keith is getting a bit romantic on us with the presumption that language use was somehow " better" in the past.

Personally what annoys me the most isn't the English as used by the Yanquis, but their common addiction to acronyms. It's not just the dumb "POTUS" " MAGA" "ICE" and so on, but wh n writing they take it as a manifestation of their own personal genius to try to invent new ones all the time without giving any reference to the reader...thus many posts you read on say, Twitter,are full of unreadable English in which you have to stop and find out whatever the dozen acronyms used in a paragraph actually refer to.
Most of the time I don't bother, as I reckon most talking this approach are involved in some kind of specialist "jive-talk", and that the acronyms are merely a way of sounding glibly knowledgeable without being found out.

And yea...I have no idea at all what the "K word" might be.