To ask why some Mumsnetters find the use of American English suspicious?

[MonaLisaDoesntSmile]

Some while back I wrote a thread under another username, and was accused by a few members to have written a fake story because I used words that are much more commonly used in the US. For the record, I learned English as a second language and my secondary school teacher was from the US, I also spent my teens watching American shows and films. 15+ years in the UK and I still use flashlight, trashcan, gas, fall, intersection and a number of other words that got stuck in my head.
I have it happen since a few times to other people- today someone decided a thread posted by a user was done by chat GTP because it sounded 'American'.
Why are people so baffled by the fact that there may be American users on the site, or people educated in the US/international American schools, or just people who have learned English with the help of American media rather than BBC?

Mum is a British word.

True, but it's also an American word and a Canadian word. Lots of Canadians use mum as do quite a few people from the Northeastern United States, especially New Englanders .

We’ll have spent a lot of time there over the last 39 years and contacts with hundreds of people… mainly NE, but in fact American BIL pointed this out to me years ago (10+?) and I have twigged it an e then. Of course not universal but … in my experience… ‘awesome’ is the ‘go to…

I met a young American on a university work placement who commented how odd they found it when people described food using a variety of words (delicious, tasty, yummy, gorgeous, amazing, tempting etc).
Where they came from, food was always simply described as ‘good’ if they liked it.
Or so they said.