Jerry Seinfeld has been there, done that: American Express - Jerry Seinfeld - YouTube
That is the tightrope that the comedian walks I guess.
I agree with what you say, if it is lazily chucked in there without skill, without the right knowing wink and nod then it’ll be a problem. The audience will sniff out your intention in a heartbeat but, if done in the right way, they’ll love the most insulting jokes you can through at them at them and that holds true for audiences across Britain and Ireland.
Calm down. I already said I was going to advise against it. I already did advise against it.
Pubkeeper? 
Having spent a decent amount of time chatting with 20-something Europeans, I can say for certain that:
- Euros like talking down Yanks.
- Euros like Yanks who talk down Yanks.
- Euros get shit-ass angry if a Yank talks down Euros.
Pick on America and you’ll do alright.
An Englishman, a Scotsman, and an Irishman are in prison. One they are all sentenced to be flogged. The warden says each one can choose something to dull the pain.
The Scotsman says “I’ll have a quart of Scots whisky.”
The Irishman says “I’ll have a quart of Irish whiskey.”
The Englishman says “I’ll have the Irishman tied onto my back.”
I think you’ll find it’s the Welsh stereotype involves sheep. If the Scots one does, then it’s only because a Scotsman’s supposed to be too mean to pay for the real thing. For a Welshman, the stereotype would have you believe a sheep* is *the real thing.
This is the best one so far!
There is a Scottish joke about Scottish people. Imagine another Robinson Crusoe character on a desert island, finally visited by a passing ship. He proudly shows the ship’s captain round all the huts he’s built out of bamboo and palm leaves or whatever, pointing out his kitchen, sleeping and living quarters and even a little kirk.
“And what’s that building over there?” asks the captain.
“Oh, that’s the kirk I don’t go to.”