British English is awash with Americanisms, but - and some of us seem to be unaware of this - there are multitudes of other such words/phrases from across the Atlantic that we have not adopted. From baseball, "a ball-park figure" seems to have caught on here recently but "out of left field" has not...or at least not so commonly
Why the difference? The reason is simple enough...we take on those things which catch our imagination or which enough of us find useful and reject those which don't. Thus, if you are seeing and hearing them in Britain, it is for one very good reason...enough of us British people actually WANT to use them!
There's no denying that "24/7", for example, is briefer and catchier than "all day every day", so we've happily added it to our repertoire. And why not? That's not to say you can't go on saying "all day every day" if you want to.
Here are ten words and ten phrases - out of multitudes - created in the USA, most of which I'd be prepared to bet virtually all of us happily use...
a) Words:
airline, babysitter, checklist, commuter, employee, gimmick, high-brow, laser, raincoat, stunt.
b) Phrases:
bank on (rely), bark up the wrong tree, hit the headlines, hold down (a job), hold your horses (wait), in the doghouse (in trouble), junk food, pull no punches, stay put, up for grabs.
And that's barely scratching the surface of our debt to Americans' verbal creativity. If you yourself don't like or have a use for any given coinage, don't use it. However, it is perfectly clear that enough of us do like some of these or have a use for them, otherwise you wouldn't be seeing/hearing them in this country, would you?
The trade is two-way as well, in that Americans adopt some of our coinages. Just to give one example, a four-letter word beginning with 's' and ending with 'g', meaning to engage in coition, has been catching on over there in recent years apparently!