The usage of since at the end of sentence tells us that the person still lives in the United States of America. While "have been to" as 5jj said that "She has been to Japan" means she no longer there. I checked Google and found ( Common Mistakes in English - Has gone to vs. Has been to). After initial research, I think the prepositions play an important role. Also, the word since can't be used with "have been to."
"Since" here works as an adverb and means "from that time till now".
More: * i have, since, been+ v.(ing)?
To sum it up, when I see the preposition to after "have been," it means that the action has been completed. On the other hand, the preposition in gives us a clear-cut answer that the action is still happening. Am I right? Will you clear it up please?
Last edited by Odessa Dawn; 31-Jan-2013 at 10:08.
A. I haven't seen you for a long time George. What have you been up to?
B: I've been in Scotland. I had a short-term contract on an oil rig.
In that sentence, 'in' is perfectly acceptable. The situation is clearly completed.