When visiting a foreign country it’s best not to:
- Pronounce the country’s citizenship publicly and loudly in a stupid and intentionally mistaken way. ie: Italianios is not a cute way of saying Italians, Cheelatoes is not Italian ice cream (gelato), it shows disregard and ignorance… unless you are 5 or 6 years old.
- Announce to locals that the food in another city was much better than the one you are in… unless your are 5 or 6 years old.
- Use language at your host’s house that is offensive to most people. ie: The “n” word when referring to black people. No excuse!
- Make an ugly face when a food you tried isn’t to your liking… unless you are 5 or 6 years old, of course. You get credit for trying it but lose the point when making a face, shaking your head and spitting it out. Time to adult and swallow it gracefully.
- Ask the waiter for a drink that is clearly regional to your area of your own country, assuming they know what it is and will have it available to you… unless your are 5 or 6 years old. ie: sweet tea.
- When advised what the customs are ahead of time regarding appropriate clothing to help you blend in and not look like an ignorant tourist with a target on your back, blatantly ignore and wear what you want… unless your mother packed for you not knowing and you have no other options.
- At your host’s home, only wash yours and your partner’s coffee cup or dirty dish leaving everything else on the counter because you didn’t dirty it. No excuse, just bad manners.
- Throw out a last minute verbal invitation to your wedding in two weeks that your host can’t possibly make. “Oh by the way you’re invited” doesn’t work for me. Ugh.
- When visiting a country rich in the Catholic religion, please don’t announce each is just another church with that Hail Mary lady when your host has gone out of their way and used vacation time from work to show you around. Why are you here?
- Tell a friend to post on Facebook (because you aren’t on it) to advise anyone going to Italy to bring salad dressing because Caesar’s and Ranch dressing aren’t offered in restaurants.
Life Notes 
Oh, God, I think I had the same house guest years ago! Clueless and doesn’t care. I’ve said before that everyone should be required to live abroad for at least a year just to get some perspective on themselves, but some people really should just stay home. You’ve got my sympathy.
I agree with you completely and sorry to hear you experienced this too. We laugh about it but we were really embarrassed to the point of nor taking them to our favorite restaurants after the first 2 days because we wanted to be able to show our faces there after they left.