It is medieval times, and mythical creatures aren't so mythical. About half of all mountain lions are griffins, which use their wings to glide over rough terrain. Dragons dwell on mountain peaks, or in deep caves. (There are sea serpents,but they are very rare, so they don't really matter). And thunderbirds ride in on oncoming storms.
Dragons feed off of pretty much anything, and they range far and wide. Their body is anywhere from the size of a komodo dragon to a buffalo (not counting their tails and wings).
My previous question about thunderbirds.
My previous question about griffins.
Note - The areas that are shaded are not part of any country for a variety of reasons. Travel through the shaded swamp is impossible. The outlined areas are the different countries. The entire map is about the size of North America, and I haven't gotten around to cities yet. (Forgive the messiness of the shading and lines, I did it on my iPad.)
Given that these creatures exist in a medieval setting, how would trade between the countries above be affected?