I know that English copies American but I imagine the opposite also happens.
Some years ago the French went nuts because of all the Americanisms people here use. They tried to invent French terms for computer language. Some exist but people still say what they like. Economics and business terms are very American too.
My Dad said neat whisky and layed off as well as getting the sack. What on earth the sack is I don't know.
We have a slang dictionary somewhere. It can be fun reading through it.
That's the American way. I did a journal a few weeks ago with some interesting observations about the different uses of words on either side of the Atlantic. Its still there if you are at all interested.
"Neat" here in the USA also is used in term as "Cool" - If Joe made a really nice piece of art that was way different than the norm, a person might say "That is so neat" Meaning "That is cool" - Our version of the English language is so crazy sometimes. LOL
I know what it means over your side of the pond, I really wondered do Americans know the English meaning?
I think a lot of US lingo has come from all the integrated people. We still have that to come as we only started to get people from other countries about 50 years ago.
I must admit to feeling a little uneasy when I see English used in strange ways. I went to elocution lessons as a young woman. Helped me a lot when I was teaching dance as I was able to project my voice over the music.
My daughter is dyslectic, yet she managed to get both English grammar and English literature certificates before leaving high school. She was terrific at Maths too (yes there is more than one number) however she is crap at computers and phones me when ever she need help. Strange really.
Also, Spanish is spoken a little different in latin countries too. In Columbia they speak spanish a bit different than in Mexico, and in Spain is a little different. The real Spanish comes from Spain in my opinion. Australia sounds different than you do in the UK and here in the states. I love learning and listening to how different countries speak their language. I don't know if you have this in UK, but here in the states, we have different accents in different parts of the country. My accent is Mason Dixon, and up here in MN it is so drawn out, yet faster on some words and sounds a lot like Canadian accent.