@International95, to answer your question–it varies. If a school had lots of international students in science and engineering programs, it would not make a difference for the OP at that school. But if a school–especially an LAC–has a good number of international students in IR/Econ/Government programs it can inform class discussions and other student learning and make a difference.
We heard from an international econ professor at a school with a similar profile that having a number of similar international/UWC students in the classroom really informed the discussion and brought in different, relevant points of view. So I think that it would be a plus at Macalester, but not everywhere.
Tufts is a good suggestion too. Chicago and Dartmouth, too. Chicago, I think, is just ridiculously competitive in RD–probably 1-2% acceptance–right now.