"In A Place" Vs. "At A Place"?

I live in America. (in is used with big places)

I live at home. (at refers to small places)

I hope I could show the difference.

Thanks

Bye

Thanks a lot for your answers. However, fadysandy, I don't think your explanation that "in" is used with big places and "at" refers to small places makes sense, as I could also say "I live in a small house" or "I live at Hyde Park". Besides, this was not my question;) But from what I read from other posts it depends on whether you are really inside a place or just at a place.
(to express to be really inside..(?)...) 
If someone's out there with another good explanation...
Btw, let's take this sentence I found on google:

Have you ever been in a place where you can't use your wireless telephone—like skiing at higher altitudes, camping in a remote area, or even shopping at the... 

Isn't it possible to use "at a place" here as well?

Tom

In fact, I would use "at" in the example above myself.

I believe that 'in' as a preposition of place is used when you are unable to disclose your precise or pinpoint location. For instance, "I live in India".
While 'at' as a preposition is used when the precise or pinpoint location is known. For instance' " I'm at McDonald's ".

Hi everyone,

I found the following link quite useful in terms of using "in a place", "at a place", or "on a place" in its correct way.

http://dictionary.cambridge.org/grammar/british-grammar/at-on-and-in-place

This simply is the best explanation to where I'm at right now.

Thanks. Useful link.