Badenoch

I wouldn't worry about it. The world is far more homogeneous than it used to be and short of a very colloquial term you'll be understood.

There are some things that may trip you up. Underground and subway mean the opposite of what they mean in NA. Pavement means the sidewalk not the roadway. Look BOTH ways when crossing the street because the cars are on the other side.

At a pub you order drinks at the bar and bring them to the table yourself. Same with food except they will bring it. Gammon steak is ham. Rocket means arugula. All desserts are pudding but not all pudding is dessert.

The good news though is that in dozens of trips to all parts of the UK when faced with confusion about a word or phrase everyone has been quite gracious in helping clear it up.

swingaling

Or Americans for that matter...

Seachain

and let's not entertain the fact that each corner of the UK has different vocabulary for everyday items that we perplex each other without even starting to worry about what yanks, kiwis, ozzies, saffas and the other lot are trying to understand! oh, and weegies.

Silver Fox

Or care.

Scots_Al

Goaguy

​​​​​I am not sure I'd recommend displaying a Trump-slogan when venturing to Europe. Better stick to something displaying the American flag or the like instead.
​​​Or perhaps I didn't get the sarcasm in your post?

Silver Fox

Perhaps?

Badenoch

Go one better. Wear a Canadian flag.

ToddSpam

definitely perhaps!!

lhrsfo

It's not only Americans who won't understand much of what is said in Glasgow. I find that I only picked up a small fraction of what Alex Salmond had to say - but then I stopped trying anyway.

stut

Don't worry about it. Silly little misunderstandings are part of the fun of travel, and you're unlikely to cause any problems by a difference in vocab.

The worst thing that usually happens is that you can get caught in an endless "you say aluminUM and we say aluminIUM LOL!" conversation.

Scots_Al

Thorgils

Actually, it's far more important, IMHO, to be alert for behavioral differences than for language differences between the two cultures. Like understanding that an impromptu queue (or line) doesn't necessarily have to extend perpendicularly from the service point you're waiting for. Intelligent queue-ers can bend the line to avoid creating access barriers to others, a concept that often seems incomprehensible in the US. As exhibit 1, I'd reference the narrow satellite terminals at ATL, where (at least in my experience, which happily hasn't included a visit now for 4 years) perpendicular lines frequently stretch across the width of the terminal, impeding passage down the center aisle of the terminal.

hipquest

Wow, I'm sorry it took me a bit to check on this thread again. I needed a laugh after my last couple of days, thank you!
So many comments, I'll just address in a general way.
DH=dear husband, most on flyertalk seem to understand and use every acronym on the planet (or have invented them?)...
As to politics, you don't talk about US politics and I won't talk UK, particularly, London politics.
I'm from the Southern US so no worries about being mistaken for a Canadian, as wonderful as they are.
I've travelled to a few places that were formerly part of the British Empire and gotten along fine (though the use of the F word, by little old ladies in Ireland, was an eye opener ).
I have friends from GB so I've been schooled a bit on some terms. I also read, a lot. BTW, the polite term in my part of the US is restroom not bathroom for public places.
@Thorgils I'm a huge believer in your line theory and your opinion of ATL.
A couple of interactions we had in Belfast inspired this question, if anybody was wondering.
So when I say y'all (and I will) and everybody laughs we'll buy another round, play the "Y'all" game and have fun.

ShopAround

I'll be in London in November and planned on wearing this: