Regarding the sources...anyone can assure you there is probably more anti-US sentiment out there than any other nation currently. The US is definitely not well-liked, and people *will* let US citizens traveling abroad know it. That would include exchange students.

Bottom line is that there are a$ everywhere, in every corner of the world, and given the chance, some will act on their feelings of ill-will. That's true of every race, religion & ethnicity. Someone somewhere has or can manufacture a reason to despise someone else, and then act on it.