Quarter note rather than crotchet.
Quarter rest if far better than crotchet rest. I've been happy to switch over mostly to British English, but with musical terms I gotta stick to my US roots
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Y'all is great in every accent -- as long as it's used in the plural. I've had some Brits use it in the singular and that's what makes it sound really weird. All Y'all is also plural, though more for big groups or adults who are annoyed at their children making enough noise for a big group ("All y'all better hush it").
Semi-Detached in the US is called a duplex (there are also triplex and quadplex), though usually the whole building is owned by one person and is partially or entirely rented out.
I can't think of any I hate, though that may because many of the American words people hate tend to be regional ones that I didn't hear much when living there (like fanny and panties, I wasn't raised with those. It was butts, underwear, and waist bags and I'm fine with all of those still).
...and while I've heard many insults for being born in the States (and my kids have had a few for just sounding slightly twangy even though they've never been), I've not heard of seppo before (google says it's Aussie rhyming slang). It did remind me that it took me a bit to get used to Brits who use Yank to mean all people from the US in a neutral way rather than an insult. I still can't really see myself as a Yank.