Most of the time I’ve spent outside the USA was in northern Italy. There are quite a few things different there that took getting used to.

1. Police - the local police in italy are known as Carabinieri, though everybody I served with called them the “Care Bears”. Traffic enforcement in local areas is done by these guys, and it’s usually in pairs. These duos usually do much of their traffic enforcement standing outside their vehicle along the side of the road. One of them has a whistle and “lollipop” (aka a handheld European stop sign). The other is armed with an Uzi. If they think you’re speeding, it’s ultimately their word against yours in court. They don’t even have to use any speed measurement devices. If it looks to them like you’re speeding….you’re speeding…period! If you refuse to stop when ordered to do so, the one with the Uzi will shoot your tires out, then they’ll come after you.
2. Line Manners - this is the one thing that irritated me to no end about italians, and it’s my understanding that Europeans, in general, tend to be this way. There seems to be no such thing as first come first served. Whether I’d be at the deli counter at Marco Polo Airport, the ticket booth for any ski resort, chair lift lines at ski resorts, or virtually anywhere else in general…there seemed to be no concept whatsoever of an organized, first-come-first-served, line. Instead, everybody would crowd around trying to be the first to get served. I was only able to hope the worker(s) would actually get to me in a timely, orderly manner. More often than not, they would just serve whoever was right in front of them first, without any care about who got there first.
3. Automobiles - Italian citizens tend to drive very small cars. The reason for this is the smaller the vehicle, the less the tax they have to pay. However, it may also be because many roads are narrow - often allowing two-way traffic in spots that are only wide enough for one vehicle at a time. While I did regularly see a Ferrari or two in the area where I was, they were otherwise still a rare site there. The vast majority of vehicles I saw were very small Fiats, Minis, and even some Ford models not seen in the USA. It was also not uncommon to see small, 3-wheeled cars that would pass more for covered go-carts than for street legal vehicles.
4. Siestas - Most small businesses close at roughly 12pm-3pm daily for Siesta. This is time intended for the shop owners/employees to go home and nap and/or have lunch with their families. While I understand the positives that come with this practice, it can certainly get frustrating when you’re on your own lunch break and want to spend it shopping.
5. Little/No Fast Food Restaurants - This is certainly not something I’ll complain about, but if you’re one who prefers familiar places to eat…well, they exist but they are few and far between. Many cities/towns don’t even have any fast food restaurants. If you’re hungry, you’ll be better off going to a dine-in restaurant or making it yourself in many cases.
6. Pizza - real Italian pizzas are considerably different from their American counterparts. The crusts tend to be thin, and most restaurants have only one size. They are normally meant for 2 people to eat as part of a full course meal, though the typical American will order one for themselves. Also, the most common type of pizza in America - pepperoni - is nothing like you’d expect in Italy. Ask for a pepperoni pizza and you’ll end up getting something that more closely resembles Canadian bacon or some other ham than the pepperonis you are accustomed to seeing in the USA. If you want an “American pepperoni” pizza, your best bet is to ask for Pizza Diavola. Also, Italian pizzas tend to be more heavy on olive oil.
7. Alcohol - when at restaurants, the joke is “if you can see over the counter, you can order it”. I really don’t know what the actual laws in Italy are with alcohol, but it’s not the least bit unusual to see an Italian kid drinking wine with their family members.
8. Modesty - Italians are definitely more care-free about nudity. Go to most Italian beaches and the women will likely not be shy at all about going topless, nor will they likely make any attempt to hide their breasts by lying face down while sunbathing. Another situation that caught me off guard involved one occasion when I was eating at one of the local restaurants. They had one of the regular public TV channels (which I recognized because of receiving the same channel where I was living) airing, but they were airing some sort of game show that had some similarities to strip poker - only they weren’t actually playing poker. I just remembered seeing a man and a woman competing on the show. The woman ended up topless and the man ended up having to take literally everything off. They network did not censor anything either. I ended up seeing not only the woman’s bear breasts, but I also got treated to a not so necessary view of the man’s fruit basket. I actually looked around to see the reactions of everybody else there - most of whom were Italian citizens - and it seemed like I was the only one in the entire building who was the least bit surprised or concerned about what was just shown. On another note, I also remembered seeing plenty of Beneton and other billboards in numerous areas that would have definitely been considered inappropriate in the USA, but were actually amusing to me and completely acceptable for the general public to see in Italy.
9. Table manners - very rarely is anything in Italy eaten with bare hands. While bread with bruscetta dip is a normal “freebie” that tends to be served automatically, much like Mexican restaurants in the USA serve chips and salsa, almost literally nothing else in Italy is eaten by hand. Not even pizzas are eaten by hand. It’s customary to use a fork and knife (or spoon). There was only one place I ever ate at in Italy where it was acceptable and expected to eat by hand - and that was at a restaurant in Aviano (the same city I was based in) which served rotisserie chicken and which also served an endless supply of peanuts.
10. Language - this is an obvious difference for an American who speaks only English. However, my friends and I often joked that “all Italians know English…but most just won’t admit they do”. I rarely ever came across a server at a restaurant who couldn’t speak English. You can also walk into virtually any shop - particularly in popular tourist destinations like Venice, Rome, Milan, etc. - and be greeted with a “Prego!” by the shopkeeper, then asked in English any questions they might decide to ask you.
11. Rain - the first time I saw it rain in Italy, it rained non-stop for 6 days. This is no exaggeration. It literally rained without any break for nearly a week. I’d never seen it rain for so long in my life. I actually began to jokingly ask when I should start building an Ark, because I was almost convinced that one might be needed. This may have been especially shocking for me personally because I grew up in the very dry Mojave Desert, where it rains maybe 3″-6″ per year.

The above list are all examples that come immediately to mind. They are listed in no particular order. I may add to the list if anything else comes up that I haven’t already considered.