Also, @Pokemontage. Sorry, but IS cheesy, especially with stuff like football player trainers. The only reason they are doing it is because America is hugely popular in Japan. America does not have any interesting mythology or folklore compared to Japan, China, Africa, European countries, South America, Australia, or...anywhere else really.
I mean, they can draw from Native American designs and mythology, which is awesome, but so far the only example of this is Wooguru.
First of all, describing it as "cheesy" makes no sense whatsoever. Nothing about B/W being based off NYC makes it tacky, gaudy, distasteful etc...because that's what "cheesy" means.
Second of all, there is nothing stopping B/W from containing Pokemon that are based on mythology from Japan or any other part of the world. Just because the region is based on America doesn't mean it will not have any Pokemon based on real life myths, cultures, traditions etc.
Example - the sarcophagus Pokemon, which obviously has it's roots in Egypt.
Example - Munna, who is based off of a Japanese incense burner and the Baku, a Japanese mythical creature.
And, as you said, Native Americans have a lot of mythology.
You also mentioned Australia, but I fail to see what makes that country any more mythological than the USA. They have aborigines who were the only inhabitants of the continent until Britain came along, just like the USA.
Third of all, what exactly is so bad about having a football playing trainer? We have Cyclists, Swimmers, Hikers, Rock Stars, Jugglers, Fire Breathers etc, so I really don't see why you would think a Quarterback is a bad idea.
Really, there is no reason to dislike it being based out of America unless you despise America for some irrational reason. America obviously has one of the largest Pokemon fanbases, and the whole premise of these games is that it takes place far away so that you can "start over." It makes perfect sense.