What would it take?
I mean, a guy could just buy some bison and let them go, roaming the countryside as feral beasts to reinhabit the landscape. It would obviously piss of landowners and farmers, and justifiably so. If there aren’t laws against it you can guaran-dam-tee our septuagenarian legislature would make laws against it and landowners/law enforcers would be given the authority to euthanize the “abandoned” animals.
I suppose a guy could slowly acquire A LOT of land and start populating his own property with bison, but the legal system would view those animals as private livestock.
I want a world where bison roam freely like other game animals and can be hunted by the general public. How does one make it happen on a broad scale? You need to start convincing landowners to take down fences, that’s for sure.