Everyone knows the whole two nations separated by a common language and the differences between elevators and lifts or suspenders and braces. But it is only after a few years do you discover other subtle differences between Americanese and English.
To the British this is a wife beater.

But in America you would be referring to this.

An observation on ageing. I had to go to a seminar in Bloomsbury. It used to be that any event I attended that had free hooch was indeed an event worth attending. These days I get just as excited when they have tea and biscuits.

Also, if in your life you can take a short cut through the British Museum, you've done something right somewhere.
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If you are American and want to instantly entertain an Englishman, say this sentence. It works in reverse too.

"There was a controversy about the albino sloth wearing macramé."