Winter driving and shoulder season driving. Snow, ice, black ice, freezing rain, slush, hydroplaning, driveway clearing, walkway maintenance, windshield scraping, and keeping an emergency kit for breakdowns. Stuff like that.

Speaking more than one language. Being from Switzerland, we're required to study 2 languages (+ our native one) at school. So it's not infrequent to encounter swiss people who speak 4+ languages

Knowing how to swim. Basic life skill in a water-rich country, but many expats can't.

We learned swimming in primary school in Germany, no opting out.

But having lived in several African countries and now in China, it's surprising how many people not only can't swim, but are deathly afraid of water.

In Australia it's not just knowing how to swim but where to swim and when. A lot of tourists drown in the ocean here because they don't know how to read the waves / don't have an understanding of the local area.

In Ontario, it’s often swimming.

Lots of lakes here, children need to be taught to swim

Italy.

Cooking, every foreign person I know eats 20x more takeout and fast food than I do.

In the dry SW US the answer is drink water when it’s 100F or worse 115F+. Having a half liter of water from the hotel for the half day mountain hike, or pounding a half gallon of ice water and throwing up five minutes later. Your body doesn’t tell you when you should drink, it tells you when you are already behind on drinking.

Dealing with winter. I live in the rural upper Midwest, where winter can hit -20 with whiteout blizzards, week-long power outages, and car-burying snowdrifts. I've seen too many people move here from warmer places and think "I guess I'll buy a warmer coat and a snow shovel", rather than "I should have a backup generator, a backup heat source, a few barrels of spare fuel, a month's worth of stockpiled food, and at least two different pieces of heavy snow-moving machinery tested to be in good working order".

Here in Switzerland the question you ask is usually, "do you ski or do you snowboard"? It's just assumed that you can do at least one.

How to walk on ice is a big one. How to cross a street is another one here in Chicago (hint: look at the cars, not the lights).

I guess here in Korea it's eating with chopsticks. In Sweden it was Swimming (especially for my Indian work mates). In Germany it was opening a beer bottle with anything you just happened to have in your hand at that time. In Poland I'm not sure, but probably making those elaborate sandwiches for parties.

If the country is big enough (aka Canada) these differences can be between provinces. People from Ontario can't ride bulls, but every kid in Alberta can. Newfoundlanders can fish but Manitobans are afraid of water. In British Columbia you are taught how to roll marijuana cigarette in high school but in Nova Scotia scotch is the bag lunch drink of choice.

Southern Georgia, USA.

This is more of a regional rationalization about occasional weather hazards. Here in coastal Georgia, we get snow from time to time, about a half an inch to two inches once every three to five years. There's a lot of people from colder climates that move here for work or retirement; they hear "a possible light dusting of snow" on the news or from a weather app and think that means nothing. Where they're from it's just normal, happens every year and there's often more. They'll even laugh at us for shutting down the schools and staying home from work for freezing rain. Here's the thing: no one here knows how to drive in snow and will likely only see black ice a dozen times in their lifetime. Further, we have no salt/sand trucks, we have no plows, we have zero civic infrastructure to meant to deal with our very occasional ice storm or light snow. It happens so infrequently that there's no way to justify spending taxpayers' money to prepare in that way for those kinds of situations. So we shut down the schools and most businesses for a day or so and everyone mostly stays home. We're not necessarily unprepared for winter weather, we just prepare in a different way that makes sense for the situation.

Just misunderstanding social cues. Where I live (Spain), there's a script you're supposed to follow for certain things and newcomers, understandably, don't understand the script. One famous example is buying new clothes. They all look great on. The idea here is that the poor person spent their hard-earned money on the new clothes. Damned right they look great on! Another would be birthdays celebrated in public venues. Perhaps someone you know is celebrating their birthday in a public venue and you had no idea they were celebrating their birthday on that day. You walk up to them and wish them a happy birthday, BUT you were not invited to this celebration. Since you weren't invited you did not come prepared with a present for the birthday person. The safe thing to do is to ignore, socialize with the people you came with, and make like that person isn't even there until they approach YOU. When and if they approach you, you make pretend you're all distracted and you have to be like, "Ahhh! I didn't see you! What's up?" The reason: that person is buying all the invitees the drinks and food. In exchange, the invitees have brought presents. It's a very nuanced and weird situation all of us have encountered. We err on the fear of not having brought a present because we had no idea because we were not invited.

Norway.

Cross country skiing. It's basically expected for every kid in school to be adaquate at cross country skiing. P. E. classes during winter could often consist of a ski trip, and a couple times per year the schools would arrange ski days with different acrivities on skis.

Cutlery.
Growing up everyone around me could use a knife and fork, whereas chopsticks were something most people couldn't use or only used badly. It never occurred to me that the opposite might be true until I shared a meal with some co-workers from mainland China and saw how clumsily they used our utensils.
It wasn't until that point that I appreciated the amount of dexterity and finesse that goes into using cutlery well, and that I took it for granted because it's something learned in childhood.

If you aren't from south / southeast Asia you'll struggle with our traffic. Our roads are a stream of everything from cycles to busses with no dedicated lanes. If you want to cross the road and can't find a zebra-crossing you gang up with other pedestrians, hold up traffic by shouting and waving, and cross.

Understanding languages you don't know - every city will have people speaking three or more languages, so you need to understand what someone is saying even if you don't speak their language. Broken English with gesturing is a lingua franca.

I'm Danish. Opening beer with a lighter or other things that aren't technically a bottle opener.

I grew up in rural Canada, but have been living in major metropolitan areas for most of my adult life. It still surprises me when I learn there are other adults that don't know how to chop wood, start a fire, work basic tools, etc.

Rural Japan.

My kids (2 and 4) can use chopsticks already. Plenty of restaurants around here where you won't see a spoon, fork or knife. (However, it's certainly possible to ask the staff for western cutlery, and in the main cities they're more likely to be prepared for that question)

Kinda reverse, but when I moved to Singapore I was amazed by how few people knew how to cook their own food. But then again you can get a meal outside for 3-5 bucks so not really an issue

Pooping in the toilet.

When I went to university with a lot of international students, there would often be poop on the seats.

My understanding is Asian toilets are different and a good few students from there were standing on the seat and aiming at the bowl from height, with mixed success.

How to stay safe in the wilderness. We get too many people that aren't from around here that think you can do a hike late in the afternoon wearing sandals and only bringing a water bottle. People don't realize that the wilderness is a dangerous place if you aren't prepared. Weather can change rapidly and you need proper clothing and footwear to account for it. Make sure you have enough time for the hike and bring the essentials just in case something happens and you need to spend a night outdoors.

Going by yourself under at least 13 is nonexistent in the United States.

The swimming lesson thing was interesting. I also assumed everyone learned how to swim in school.

Pronouncing local place names. Lots of scattered areas here with place names that are spelled like other places names (for example we got a town called Egypt, a town called Binghamton, etc.) except that they're all pronounced differently. For example, we have a town called Leicester, named after the actual Leicester, and locals tend to raise an eyebrow when someone asks "how do you get to lester" (that would be the normal way to pronounce it)?

"Who's Lester? Is he the new guy in town?"

"What? No, the town."

"That's Leesester, not Lester."

"I'm sorry, wut?"

I of course just add to the confusion if I'm the one to break the news, as I have a Kiwi accent, which is atypical around here. So it becomes a "what do you know" kind of interaction.

Male being good at talking and flirting with girls. Where I grew up (south of Italy) you have to be able to know what to do as a young heterosexual man, otherwise girls would completely ignore you. When I was young, italian girls expected "work" from boys, a lot of work. You could not throw money or take shortcuts (I don't know if it is still valid).

When I moved to north of Europe, in 3 different countries, I realized that for north european guys existing was enough to get many girls. It was so easy, girls flirt with you, they literally go after boys. You could do nothing and a girl would start flirting with you. And being decent at talking with girls meant that any average Italian guy abroad was a Don Giovanni.

Hiking and basic wilderness knowledge.

I live in the Mojave Desert. Simple stuff like knowing not to cut through bushes, wearing proper shoes, avoiding feral dogs, and always having something to defend yourself with when walking in the desert aren't common among a lot of people who aren't originally from here.

Driving. Moved here from Bangladesh to UK. I did a big mistake by not learning to drive in my country. Now its too expensive here to learn. Here driving is required if you want regular job well paying jobs. Don't be like me. Learn how to drive.

I always think it’s weird when I run into people that can’t whistle or make a horn sound blowing a blade of grass. I’m not even talking like those ear-piercing 2-fingers-in-mouth whistles, just regular Andy Griffith style.

Definitely understand there are many whistling taboos(as there should be, Russia) and some bored rural-ness that factor in.

In my immediate surroundings: small-scale farming. The old folks all know how to run a few goats and sheep, will have a few pigs and chickens, a vegetable garden, some fruit and olive trees, grapes, small fields. Once you figure it out you can feed yourself comfortably, but it's a steep learning curve if you didn't grow up with it. Quite a few foreigners who move in because they dream of self-sufficiency overload themselves with new stuff and become overwhelmed. I still can't compete with my neighbors at gardening after 20 years but I'm getting the hang of it.

Can't ride a bicycle in my area without very insanely high risk of death. You don't see bikes on roads at all. None of my kids know how to ride. Ive ridden vast distances though. Makes me very sad.