The countries around the world that you cannot flush toilet paper in are the countries of Turkey, Greece, Beijing, Macedonia, Montenegro, Morocco, Bulgaria, Egypt and the Ukraine.
If you are traveling to any of those countries you must not flush toilet paper down the toilets there and instead throw the toilet paper away.
However nobody is gonna really know it if you did flush some toilet paper down the toilet in those countries but the public restrooms in those countries have a sign forbidding you from flushing toilet paper down the toilet.
It's because the sewer systems in those countries are not as great like they are in the United States but I would think that if human waste can go down those sewer pipes that toilet paper which dissolves should go down the toilet with ease as well.