This is an alternate world. Japan and the US do not exist.
Have a look at this article http://bulbapedia.bulbagarden.net/wiki/Pok%C3%A9mon_world_in_relation_to_the_real_world
In particular, these two entries; -Lt. Surge is known as "The Lightning American!" -A Guitarist that can be battled in the Battle Frontier mentions that his guitar is actually a Japanese instrument.
Both mention America and Japan, so both countries exsist in the game world. We don't know for sure if Gens 1 - 4 are set in Japan, and gen 5 in the US, but with all the facts we do have I say it's a pretty good guess.
This is the most interesting topic I have read on this board ever...curse you fools for trying to extinguish his creativity for reasons I can only assume are related to jealousy...
Right on TC, I like it...
^ This, there is about as much creativity and imagination on the Gfaqs board as there is in a THQ conference. Not many will give you props for this.
I think it is rather believable and your points are coherent and make sense, no one else can debunk any of them. I honestly wouldn't think twice about the Japanese thinking this a way to "get back" at the US.