Because the entire Anime industry is owned exclusively by the Government of the country of Japan.

So ignoring all the logical shortfallings of this question:

No, they shouldn't ban Hollywood from Anime. The Avatar movie introduced loads of people to the Anime itself. The movies aren't made to appease to die-hard fans, they're made for a broader audience and some of that audience may in turn, end up checking out the source it was based off. This isn't a bad thing.