Just had a discussion with a colleague, and of course I came here for a definitive answer.
He said that when you end a sentence with “U.S.”, you can’t use a double period, e.g. I live in the U.S…
However, I said you do use punctuation with the final period, such as:
I live in the U.S., but I came from Korea.
You live in the U.S.?
So why not “U.S…”?
Personally, I think it would look very odd to have:
I live in the U.S. I like the U.S.
vs.
I live in the U.S… I like the U.S…
My source is the Chicago Manual of Style, which is the standard for general book publishing in the United States.
First of all, notice what I did in the preceding sentence. According to Chicago, “United States” is properly used for the noun form, and “U.S.” is commonly used as an adjective. So:
I live in the United States.
but
Please change this Canadian money into U.S. currency.
Second, Chicago (and common sense, IMHO) prohibits double periods when a sentence ends with an abbreviation that takes a period. The single period stands in for both functions. But a period cannot also serve as a comma, question mark, etc., hence their use.
It looks like this type of convention happens often enough that there’s even a word for it (haplography).