Yes. Check validity needs and other details here: https://travel.state.gov/content/travel/en/international-travel/International-Travel-Country-Information-Pages.html
No, if you have a USA passport. You can be in Italy and San Marino for 90 days. But, you NEED a return ticket to enter the country. Make sure you don't need a visa for any countries you are traveling through. You may need it even if you remain at the airport. You can check here: https://travel.state.gov/content/travel/en/international-travel/International-Travel-Country-Information-Pages.html
Euro. You can usually exchange at your bank ahead of time if you prefer to carry a lot of cash. I recommend checking with your bank and credit card companies. A lot of times they allow foreign transactions or ATM withdrawal but watch out for any fees associated with this. If you do exchange currency once there I would avoid doing this at the airport as the fees are higher. Also, make sure you alert your bank and credit cards of your travel plans so your account is not unexpectedly blocked while your traveling.
Yes. But, the wine is better.
No. More people than you may think speak at least a little English. Especially within airports, train stations, etc. But, a little try goes a long way with Italians. Don't be afraid to try a word here and there or at least say thank you "Grazie" they'll appreciate it and be more inclined to help you. Google translate app on your phone is also great!
You need it. Take it with you and save it for at least the day. Basically, this is how they ensure businesses are paying taxes. An officer can stop you after leaving a store and ask to see your receipt. If stopped and you don't have it both you and the store will get a ticket.
Yes. You can find these adapters almost anywhere. You'll want to look for the ones for "Europe".
Check with your provider. They may have a good international plan available. I recommend downloading WhatsApp for messaging since you can use this service for calls and texts over wifi.
Pay attention to the parking line colors. They mean different things than they do in the US: White Lines = Free Blue Lines = Pay Yellow Lines = Handicapped or Time restricted Additionally, people seem to park basically wherever they want when there are no lines. And parking can be tighter than NYC at times. So just do your best to use your judgment. Look at other cars and use that as an example.
Be sure to check any rules/regulations of the airline you choose, and the countries you are traveling through/to.
You are allowed to drink alcohol everywhere. Yes, everywhere (Except when driving. We don't condone that and neither does San Marino). So, grab a drink and go for a walk around the city.
It's a bidet, it's lovely, and once you use it you won't understand why these aren't commonplace in America. https://youtu.be/fPeRXapDfsw Generally, this video covers the basics. A Few things to note: 1. There should be soap there so it's more than just a rinse 2. There is a soft towel hanging over or near it that you use to dry yourself after. Don't confuse it for the hand towel and don't use toilet paper! 3. Sometimes this is just a hose and nozzle located next to the toilet bowl instead of a separate bowl. 4. You can either face the faucet or face away from it. Don't be shy to just ask us how this works! It's amazing.
Recycle. It's very important here - It's Important everywhere! - But, San Marino is very sensitive to this topic. Everywhere you go you should have the option to separate your waste appropriately. Please do so. Do not dispose of any personal hygiene products in the toilet: This should really go without saying as this should apply in America also but, it's a bigger deal in Italy and San Marino. You will cause a major issue with the sewage system. So, dispose of any products accordingly in the garbage provided.