People ~love~ perpetuating clichés about other countries. In fact, one country that often feels the brunt of this is the United Kingdom (usually at the hands of Americans, no less).
OP kicked things off with...
1. "It irritates me when others (particularly Americans) go on about British food being terrible."
"I've traveled the world, and I think our cuisine is much better and more varied than a lot of places."
"The food thing is purely from WW2 when American soldiers were stationed here, and we had rationing, and the country was slowly starving to death. So, of course, the food was bad.
"American food is actually terrible though. They can't even get cheese right, and everything is loaded with soy and seed oils."
"Agreed there. I went to New York a few years ago and was really looking forward to the food 'cause it always looked good on TV. Was I disappointed? Hell yeah. It was just all so sweet and had no flavor, and we went to quite a few places, and all of it was like that. ... And what the hell is up with their butter? That ain't butter, LOL!"
"Man, I hate this one, and I’ve seen enough Americans in person to know that many of them also have very awful teeth."
"We (at least in Scotland) get free dentistry until we're 26. Not that many people have bad teeth."
"This one annoys me, too. Our teeth are pretty healthy compared to the rest of the world. The myth largely stems from the extent of teeth whitening and straightening in the US; whereas, here, if your teeth are healthy but a little wonky or yellowed, no one really cares."
"What does that even mean? Like Geordie? Scouse? Cockney? Yorkshire? Brummie? Welsh? Glaswegian?"
"It always somewhat spoils a TV show I'm enjoying when they introduce a British character and go for the ridiculous accent and saying shit like 'golly' 🤣."
4. "That we’re obsessed with tea."
"It’s just a drink some people have at home. Look at our high streets; we have coffee shops and pubs. You don’t see very many tea bars, even the tea that you see for sale in coffee shops is rarely bought compared to the coffee."
5. "The weather thing."
"Pretty much all of western Europe and large parts of the US have the same or even shittier weather."
"London and the east coast get less rain than most of northern Europe. Whilst we're at it, London isn't foggy. The geographical conditions for fog are not present there."
"I quit Twitter because of this — the British social media class seems to think it’s quirky and funny to be miserable and anxious about everything."
7. "That we’re somehow oppressed as a nation by our government."
"Yet, they (Americans) can’t legally cross the road unless at a pedestrian crossing LOL."
"As a Brit living in Germany, can confirm we have massive road crossing freedoms in the UK!"
8. "When people say Brits love queueing, waiting, and standing in line???"
"Just because people form an orderly queue at the bank doesn't mean we're excited about it."
9. "That we are all reserved, stiff upper lip types who wouldn't say boo to a goose."
"Some of us are, of course, but a quick trip to any town center on a Saturday night would quickly disabuse you of that opinion. It's a lazy, boring trope; we are not all stuttering Hugh Grant wannabes."
10. "That 'Bri'ish' thing."
"Yes some people drop the 'T', it's not everyone. And I fucking HATE hearing it in the media, broadcast to millions. But the thing that really just irritates me about the whole issue is that Americans do it, too, just differently. The American version would be 'Briddish,' because they replace their 'T's' with a 'D' sound."
11. "That we are all 'god bless the Queen!'"
"Er...no, cheers. We mostly don't really care."
"I always find it funny that news about the Queen is often more popular in the US than the UK."
12. "That we need a license to do anything."
"America has far worse occupational licensing restrictions."
13. "That we drink warm beer."
"What's even worse about this is that plenty of British people also think ale is served warm because it's been said so often. Ale should be cellar temp (9-11°C)."
14. "People not being friendly/not talking in public."
"I’ve lived in Glasgow all my days (definitely a big city) and genuinely never found this to be an issue. You’ll get the odd arsehole, of course, but if you’re needing help getting somewhere, etc., never had any issues."
"This. I'm French and have been living in the UK for years. I always found it far easier to have conversations with complete strangers in the UK than in France."
"I work for a company that has offices around the world, including one in the US, but our UK office is in Cambridge. The number of times I hear people from the US office ask about the 'London office.'"
"I’ve got a Scottish friend from school, and I can understand her perfectly. I can also understand her sister, too. So yeah, that’s complete bollocks."
Note: Some responses have been edited for length and/or clarity.