What are the thing you should not do in America?

Things you should not do in America:

-Stand closer than about 40 centimeters from an American you are speaking with if you aren't related to them, or in a romantic relationship with them

-Use "the n-word" (nigger).  

-Talk openly about scatological topics in polite company (basically, polite = mixed gender and age, as a rough rule of thumb).  Part of the American concept of politeness is being prudish and discreet about those topics.  Yes, everyone does them, we are all human animals who excrete the same substances.   But it's just not polite by American standards to talk about it.

-Refuse to tip in sit-down restaurants where you are provided with a bill for the meal.  Double the tax, and you will be fine.  Yes, this is a weird, archaic, and deeply inegalitarian custom.   Slowly, very slowly, it may be starting to end.  In the meantime, you are, unfortunately, providing part of what your server depends on to earn a living, as by law restaurants can pay less than the jurisdiction's general minimum wage if their servers make up the difference in tips. 

-Call an American girl or woman a "cunt".   This is a cultural difference between the US and (most of?) the rest of the Anglosphere.   In the US it is primarily a viscerally gendered, misogynistic word.  

- Irene Colthurst, Observant of the Drama