Re: How should non-native speakers call the United States in casual conversations?
Personally, I try not to use "America" to talk about the US, since America is far larger than the US alone, and even in the US there are people aware of that fact. 

Originally Posted by
billmcd
Context, of course, and the person to whom you are speaking would suggest the term to use, but in general, any of those terms are OK. I would use "the U.S." if I were from another country and speaking to a native American.
And what would you use if you were talking to a WASP, or an Afro-American, an Asian-American...? 
Greetings,
charliedeut
Please be aware that I'm neither a native English speaker nor (at present) a teacher.