[Symbiote]

I live in Denmark, and for such basic words (crisps, trousers, maths, aluminium, football, quid, couldn't care less, fire engine, motorway, petrol, public transport, railway, tram) I use my native British words.

People occasionally comment that it's a British word, but being misunderstood is so unusual I can't remember a recent example. Essentially everyone has read/watched Harry Potter, Dr Who or Midsomer Murders, and Europeans are probably ten times more likely to have visited the UK as the USA.

[drnick1]

Fire engine and railway aren't specifically British. There are much better words like boffin, or my favorite, bellend.

[Vinnl]

Wait, "couldn't care less" is British?

[Symbiote]

Many/most Americans say something like "I could care less about the World Cup".

British people say "I couldn't care less about the World Cup".

Both are saying they have no interest at all in the World Cup. I don't know why Americans phrase it that way.

To give a documented example, the lyrics of Teenagers by My Chemical Romance:

    They said, "All teenagers scare the livin' shit out of me"
    They could care less as long as someone'll bleed

[HardlyCognizant]

I always assumed the American version was using "could" ironically. Now I'm wonder if is an unintentional neologism.

[Vinnl]

Ah, I'd heard that latter one, but I thought that was just a mistake in the sense of "could of". TIL!

[gnubison]

I think everyone says “couldn’t care less”. But Wiktionary does say “could care less” is “American, nonstandard, proscribed”, so I guess only Americans have that (defective) alternative phrase.

[petepete]

There are a few things like that which stand out when I'm watching/listening to American media.

Another is 'on accident'.