One can find wild Bison in part of Canada and USA too, they are by no means rare, you are referring to the European Bison. I understand there are some living in the wilderness of Belarus and heard that Poland was allow commercial logging in some of the forests which would be prime Bison habitat. It's sort of sad what we have done to the habitat of these creatures. Hopefully they let some out of the paddocks to roam European forests once again.