I’m not sure where ‘here’ is, but in Afghanistan, it’s the Americanswho have been farting inappropriately.
I did mentioon noisily hoicking up great gobs of phlegm in the morning. That’s something to be avoided.
Yeah I was gonna mention that in the post but I didn’t want my point to be lost.
A guy once brought back a Japanese omamori (good luck pouch) with a prominent Manji on it to a Jewish friend of mine. She didn’t think anything of it, being into Japanese culture herself. Her parents were not amused, however 
I’m surprised no one’s mentioned Americans’ hang-ups about nudity. Compared, at least, to some European countries, Americans are very sensitive indeed about baring too much skin: witness the upset over Janet Jackson’s “wardrobe malfunction” a few years back. Guys visiting the US should know that a Speedo is awkward at best at the pool; women should know that on most beaches you can’t go topless. A German teacher once tole my class about how upset some American friends got when she let her toddler swim naked at a local pool.
Not so much a cultural hang up, but a difference. In plenty of countries used toilet paper is not to be flushed. Since I live very near Mexico there’ve been plenty of times I’ve entered a bathroom to find used tissue (blech x 1000) in the trash or on the floor.
Also, a glass of water, or food washed with water from the tap, won’t be touched. It’s not that your guest thinks your kitchen is dirty, just that tap water back home isn’t clean enough for consumption.
I’m still not used to having my cheeks pinched by complete strangers, comments made about my tragically pale skin or hearing someone affectionately called the equivalent of ‘Fatso.’ Being a chubby white kid made walking down the street painful in more than one way.
I’m not saying it’s universal. Just males in close proximity, like in a booth leaning in, or talking in a library. Any further apart than that and I take it back. Here’s what Deborah Tanner has to say on the subject:
So, are you in the US? Not to pick on you in particular, but this is an example of where ignoring the OP’s explicit question (if indeed you are doing so) comes across as confusing. I’ve never seen the latter two items anywhere in the US, even somewhat close to Mexico.
In America, it is rude to ask about money. ‘how much do you earn?’
In Britain/Ireland, it can be rude to ask nosey questions which could be seen as ferreting out the social status of the other person (where are you from? how much do you earn? what car do you drive? what’s your job? where did you go to school?)
In America, it’s a bit rude not to ask personal questions of a person you’ve just met. It can come across as a bit cold and reserved.
pdts
Of these only “How much do you earn?” would really be unacceptable here, I rarely know what even close friends are getting.
The others can be asked in a seemingly rude context but aren’t on the face of it verboten. For example, most Irish people wouldn’t give a shit if you asked them where they were from, but a lot of people here who are obviously of a different ethnicity get sick of being asked that same question over and over.
What about asking about someone’s religion? Working out here in Asia, I once had a coworker who came from Northern Ireland, and he was quite taken aback when I asked him casually, “so, are you Catholic or Protestant?” and he instructed me never to ask that of a Northern Irish person again if I knew what was good for me, unless I had a good reason or knew them really well. (I know that Ireland <> Northern Ireland, but I was curious.) In the US such a question might be construed as a bit nosy, but not shocking. In Taiwan it’s no big thing at all AFAIK.
OTOH he had a broom up his posterior about a lot of other things, so it might have been an individual quirk.
I’m not sure a stranger asking that would offend anyone even in Northern Ireland, but down here the majority of people are Catholic (at least nominally) and offence might be taken by some because you imagined they could be a Protestant. 
We have more-or-less a “don’t ask, don’t tell” policy about religion in Canada (well, the parts I’ve lived in, anyway) - it’s basically considered private, and you just don’t go there. All the stories I hear on the Dope about people getting grilled about their religious beliefs boggle my mind - it just isn’t anyone else’s business.
We do always ask where someone is from, though. Either you’re from a different part of Canada, or a different part of the world.
One thing that I’ve found, especially from Asian countries, is that they don’t realize that if an American says “What’s wrong/Are you mad/Is something upsetting you?” We want to know. We’re not asking for no reason, we’re asking because it’s apparent to us that’s something’s going on. If you say no, and especially if you say no TWICE after we’ve asked again, then we’re going to assume that nothing is wrong or you don’t want to speak about it. We’re not going to probe and try to guess what’s wrong and SAY exactly what’s wrong just so that you can say ‘yes that’s it’. I can’t even tell you how long it took me to figure that one out the first time I ran into it.
Which reminds me of something else we’ve mentioned in these threads before: for most Americans, “how are you?” means “hello”, not “please tell me how you are feeling and how your weekend was”.
Do they ever come back with, “If you loved me I wouldn’t have to tell you?”
By golly I’d forgotten that.
The perspective in New Zealand and Australia is different however. Like Americans we generally mean it when we suggest a person should visit.
I have British friends who now live in NZ. The first time they were invited by work colleagues to a barbeque, they misunderstood thinking it was a polite but empty invitation. The phone rang at 6:30pm asking where they were…
However, if you are me then even if those without food are encouraging you to start you still wait. I see the encouragement as part of the social dance, something that is expected to be said but not expected to be acted upon.
Some people are weird about food being ABSOLUTELY PIPING HOT. My mother is convinced that if it isn’t served on a hot plate and you don’t started within seconds of its arrival on the table then it is ABSOLUTELY RUINED.
Do not make negative comments about food someone else is eating, unless you know them very well.
Comments on weight are likewise restricted to people you know very well, unless it’s a comment on how someone has lost weight.
Questions about when you’re going to get married or have kids are also restricted to people you know very well.
As Dave Barry once said, “You should never say anything to a woman that even remotely suggests she’s pregnant unless you can see an actual baby emerging from her at that moment”, or unless she has told you she’s pregnant.
If you asked an Irish person a string of those questions when you first met them, I’m pretty sure they’d get peeved quickly.
pdts