As far as I know, this phrase is only found in Korean(=갔다오다) and Japanese(= 行ってくる). It literally means, like Claire mentioned aboved, "I went to America for a reason like a trip or visiting somebody and just got back to my country" meaning you are in other places at least not in America now.^^/ I think it comes from the difference of grammatical structure. It'd mean "I have been to America" in English. \^o^/

It means you go to the United states for a while and then come back after fullfilling your purpose.