@McTag,
Bison also live in Eastern Europe today , and once lived all over Europe and Asia along with other Bison and Bubolus and Bos species . Bison are direct close genetic relatives of the GAur (which is the Asian Buffalo). So the distinction , in cladistic terms, begins to fade and the only distinction that really makes sense to us is the "buffalo cheeses' that are made from a subspecies from Italy. (Nobody makes cheese from bison milk, they are just too stupid to not kill you by their sheer mass).
I can be convinced on the sepparation of the term but, like rabbit and "hare" the actual distinctions are few and relatively unimportant. Like the word "camel" includes Llama, Bactrian, Dromedary, Guanaco, Vicuna,Alpaca etc , its asort of "family" name that cladistics nuts like to lump together rather than split apart.
In biology, we are now in an age of "lumping" rather than "splitting". Splitting into distinst and smaller subdivisions is acvtually kind of Creationist , when actually, we now can see the genetic similarities of lots of animal;s and plants