I agree. We have enough movies and games that are US-centered, we don't need Pokémon to be one of them. But here Hawaii is a particular part of the US, it's not as if they chose California, Texas or Florida. Having a region that is a true archipelago has a great potential and it's fresh. Although the overwold needs to stay linked within its boundaries. The thing not to do is basically the islands from FireRed/GreenLeaf.
California would be a great, choice, though. We're pretty much a cornucopia of environments.