When I first moved here in 1986, things were so much different to Los Angeles, that it really WAS a shock. I came on my own at 17 for a gap year before starting uni (and never actually went home

) and, back then, England was a totally different place.
Everything was different. Everything.
Cars, light switches, toilet flushes, sockets and plugs, kettles (I remember being perplexed by someone's plastic kettle. How do you put a plastic kettle on a hob?), door handles, televisions, carpets, curtains, duvets (I'd never seen one before), off licenses (what the hell did that mean, anyway, and where were the ON licenses?), fashion, hair styles, shampoo...
And then there was stuff you didn't get in LA: chip shops, pubs (and all the related eccentricities involved with their opening hours), bakeries that sold savoury food, sausage rolls, working men's clubs, weird telephone dialling codes based on where you were calling FROM, the 24 hour clock, half day opening on Wednesdays...
And then the stuff that was just plain missing: malls, all my favourite clothes shops, the ability to just walk into a bank and cash a cheque, cable tv (England had 3 channels when I moved here, and NONE of them were 24 hours), MTV, customer service, etc...
Don't even get me started on the new vocabulary. Sometimes it felt like I was speaking Chinese. What's a bap? Or a buttie? Or a cob?
And then there were the words that meant something entirely different:
America: three musketeers bar. England: milky way
America: milky way. England: mars bar
America: mars bar. England: no such thing.
America: snickers. England: marathon
America: marathon. England: curly wurly
I'm still have to resort to long descriptions and hand gestures to buy notebooks, files and binders.
Those are just the non-humiliating examples. I learned the hard way that "fanny" refers to an entirely different part of the female anatomy.

And then, that's not even to mention learning about "piss-taking". Where I come from, you're nice to everyone, whether you like them or not. Here, you're nice to people you don't know or don't like and "take the piss out of" people you DO like.
I couldn't figure out why people who'd been so nice started saying hurtful things. I was bullied terribly at school, and the one thing in the world I hate most to this day is being laughed at. Imagine when your friends start doing it. It took me a while to realize it's a sign of affection LOL It means they feel comfortable with you and are secure in your relationship.
TBH, I think the UK is much more "transatlantic" than it used to be, but judging by how much trouble I have in the US finding things, I can't believe it's entirely easy for newbies to the UK even now.