You mean the phrase 'fellow traveller' that you love to quote.
That would be one.
I've also had problems over using "febrile", "nebulous" & "incontrovertible".
You have been told it is not a phrase in common parlance in the UK. Indeed it is an American expression.
You'll find it used in British newspapers.
You'll find it defined in British dictionaries without any reference to it being US English only.
And you'll also find that many terms which were originally or are mainly American are both understood and used here, e.g.:
"How are you?" "
I'm good, thanks".
"What would you like?" "
Can I get a....."
And lastly you'll find that people also know and understand American words which we don't use here, such as
sidewalk.
So not surprisingly, intelligent people understand the phrase to mean a slur on travellers.
Even if that was an intelligent reaction, it cannot possibly remain so after their ignorance has been remedied.
And yet over and over again, after the meaning had been explained, I still got people accusing me of using it as a slur.
What is surprising is when a person on here who claims he is intelligent, can't grasp why he uses an expression not in use in this country.
But it is used here.
I've known it for so long I can't remember when I first heard it.
It may be
less commonly used here than in the US, but it is absolutely not "not in use".
Have you considered it may be you at fault
Have you considered that if I use a word or a phrase which as far as I am concerned is a perfectly normal, understandable one, part of any normal vocabulary, and that turns out not to be the case, it is not my fault that people don't know it?