There is much less difference between British and American English than most people imagine.
What is grammatically correct in the UK is also correct in the US, and vice versa.
With the exception of the spelling of a few words, and the obvious differences in pronunciation, idiomatic expressions, and lexical items, good English is good English, and bad English is bad English.
Chalking things up to British/ American differences is most often the sign of ignorance.
So, ESL learners, beware!
It's one thing for learners in this forum, with little exposure to English in their everyday conversations, to fear the spectre of some vast 'difference' between American and British English they hear about.
It is another for native speakers in this forum to construe poor grammar as being a valid American variant, and some normal evolution of 'the people's language'.
As for the evolution of the language, and what actually constitutes poor grammar, those are topics for another place.
The Third Way
When I was a childe, people complained about the changes coming from AmE, but now it appears that the position has reversed.