What topics of conversation are considered taboo in America that aren't in other countries? Why?

The one thing you can't say to an American: "You're fat"

I have to agree with Ashley Timms.

Talking directly about weight and people's bodies isn't exactly taboo, but whenever I've traveled ( and my mom reports the same) we are astounded at how people will call people fat to their face, or comment on how big your butt is, or your fat legs. I get that it's a custom difference but it's jarring. (China, Mexico, parts of the UK)

There are so many subcultures of the US, so to try and make a generalization is tough.  I certainly have had people comment on my weight in the US, and it often is particular to certain cultural groups.  Sometimes, it's obvious that the comments are meant to be complimentary. But in the informal parts of the workplace, it's easier for me to say, hey: back off, rather than when I'm a tourist in another country.

Here's the thing: I am 5 foot 9. My weight fluctuates. Even at a normal BMI I have very wide hips, and a big bum.  Combine that with being tall  and I  have never been seen as petite. People from Asian countries seem the most preoccupied with me being a non petite woman.  I am now taller than both my parents. ( They've shrunk)  I also have a bust, which has been commented on a lot.

I will admit to being sensitive. But overall,  I don't find that Americans are in the habit of saying " You've gained weight" to your face. 

They'll say it behind your back, as soon as you leave. ;)

Another issue is but a topic but having young kids be naked is a bigger deal in the US. My husbands family is from the UK originally, and I'd let my young kids walk around naked. But it really bugs some people out in the US.

I have to admit, I'd be one of the Americans who doesn't know what to do with her eyes at a nude beach. But I'm not opposed to the idea.
The subject of tipping in America is the nearest a mundane activity could be to a holy war. Opinions on the topic are so heated that many see bringing it up like bringing up abortion or the death penalty; it's that rude. A few people will even hate you if you disagree with them. Hate, as in seeing you as barbaric and evil.

Why is this single transaction, out of dozens of customs with similar impact, so sensitive? I'm not sure. Somehow it has become the convergence point of all your opinions on labor relations, etiquette, the minimum wage, professionalism, the free market, social responsibility, justice, freedom, kindness, and morality. How you tip is who you are. Bring up the question at the end of your next dinner party and see what happens (or don't).

Obviously, not all Americans are this heated about tipping, but it's a large enough contingent that a prudent citizen must be tight-lipped around strangers. 

I doubt it's this severe anywhere else.
Not sure if this is really a "topic," but:

Referring to a person's racial or ethnic appearance when describing them physically. There is not uniform agreement on this.

The situation: you are at a large gathering of people with your friend Susan when you spot your other friend Mark on the other side of the room. You point him out to Susan, who has not met him. In this situation some people might accelerate the description process by telling Susan "He's over there by the door -- the black guy with the glasses," if Mark is one of few black people in the group. Other people will avoid referencing Mark's skin color, sometimes going to great lengths to say "he's the guy in the red shirt, no, the OTHER guy in the red shirt, with the darker jeans...".

My sense is that white Americans tend to do the latter approach more than people of color, I think out of a sense that it is inappropriate to call attention to people's race in any and all circumstances. It seems a little ironic, because all the people of color I have talked to about this phenomenon have the same sort of amused reaction: "dude, it's okay, you're not oppressing me if you just point out that I'm black/Indian/Latina. No need to describe what I'm wearing for twenty minutes."

I'd be curious to hear from others on this issue.

Lack of success or failure.

Unless there is a heartwarming uplift in the end, it is avoided.

"My brother is in jail. He's a rapist."

"My kid was hit by a car last year and I need to spend every waking hour caring for him."

"I got laid off. My training is no longer relevant and I'm 50."

That makes everyone go silent. Americans don't mind failure as long as there is a turnaround or hope for a turn around. Your rapist brother has no real potential upside. The kid hit by a car ain't going to get better. Retraining at 50 is unlikely, especially for an idiot like you.

You'll hear Americans desperately try to turn it around and look for an upside. The British and French wouldn't. The Germans would just nod knowingly and be your companion. Americans will try to fix it. THERE MUST BE SOMETHING THAT CAN BE DONE! Together we'll beat this!

So, knowing it is taboo, Americans don't discuss irredeemable failure. It's taboo. You don't even know about it. That's one of the reasons behind the taboo surrounding death (you cannot fix it...but we're working on it!) and how much money you earn (probably not enough to show you're winning and awesome). You don't ask someone how much money they earn either, because that might place them in a sticky situation of having to look for an upside about their shitty salary.

I was catching up with a friend whom I've known for 30 years. I'd been tracking him on Facebook and what not. About 2 hours into the conversation I discover he's been divorced for a couple of years...but he broached it by selling the upside of a shorter commute among other things!

I am comparing Guyana to America.
  • Weight. People in America and in general in Western countries do not discuss their weight and it is taboo to say someone is getting fat. In the West Indies people do not care and will tell someone that they are fat. For example my Guyanese uncle told his daughter (Canadian born and raised) that she was fat and she was insulted. He didn't understand why.
  • In general there is just not a need to be as "politically correct" as there is here. Pretty much anything is fair game. For example I've rarely heard a Guyanese person say "passed away" instead of "died" or "dead". I remember another example about my Jamaican neighbor. He invited his childhood friends over for to play basketball and they were in the house getting water. His younger sister was there, and he left the room to do something. His grandmother was there and said "Don't leave them in here with her! They'll rape her!".
  • Edit: I found a video that shows the kind of embarassing stuff West Indian parents will say in front of your SO. I could totally see my relatives doing like this video and discussing dirty underwear or something like that.

I think that one of the reasons we loved Seinfeld is that the characters talked openly about sex, about their sex lives yada, yada, yada.  As  an American of Nordic Heritage, I have never met another human being who talks about sex like the cast of Seinfeld.. In fact, I'm not sure how this whole demographic procreates.  The French, on the other hand . . . .

I have five brothers and sisters and suspect that some are quite wealthy and some are quite poor.  But we will never have a conversation about money; we'd almost rather talk about sex than money.  My mother, who occasionally did talk about her sex life actually talks about her money and loves showing off her balances; that concerns me.  One thing I know about her; she never talks about death even though she is 90 and has lost almost all of her friends.  They didn't die; she just lost them.  That's what happens in a world where death is a taboo.

Other than sex, money and death, we have no taboos.  Except politics and religion, but then we'd never admit that.
How much money you earn, dialogues  about race and ethnicity, many people are quite uncomfortable with their "negative" emotions here, so anger, sadness, fear, etc are often a taboo subject and are expressed another way.
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