I never heard of Native American casinos, is that even exist?
Its basically down to tax laws and so on, same reason a territory is significantly different to a US state and many live the majority of their time there for the tax benefits. I dont know their character is especially different, its done for the legal advantages that they possess.
Canada has the same deal, anywhere laws might vary its a thing. Gambling boats used to be a thing, they sail into international waters and play the game legally that way but I've no idea how viable each idea is right now as it varies over time and I thought USA has loosened up slightly.
controversial due to the opposition of the locals.
I can understand religious reasons but that means you dont partake personally. Do casinos cause any crime or negatives to a community really, so long as the management works to exclude those with some kind of problem gambling its just gaming imo.