We could breed far more Buffalo but where would they roam? Yellowstone can only support so many and unless the Government wants to put huge tracts of fenced land aside for them, the Buff will end up crossing highways and roads.
The Enviros used to have plan for a Buffalo Commons for the Midwest. It is probably still on the books for when depopulation occurs.
Well, roaming is somewhat limited as ranches are now fenced. But, actually Buffalo are now commercially raised for their meat. It can bought in grocery stores and it can be found in certain restaurants. Safe to say the American bison is no longer in danger of extinction.