Hrm maybe Japanese people don't like what the 360 offers them over the PS3 in terms of exclusives which is mainly a few failing JRPGs, shooters, Fable and Alan Wake. I'm not saying the 360 doesn't have exclusives, but maybe those exclusives don't appeal to the Japanese gamer, just maybe?
The PS3 exclusives of FF13 (in Japan), Yakuza series, and Demon Souls may fare better with that audience. Throw in the blu ray thing (might not be a big deal to them) and the DVR add-on (which seems to be selling pretty well) and the only thing that the 360 has over the PS3 to the Japanese gamer are a few exclusives that they don't care too much about, XBL and entry level price.
Contrast that to USA where the exclusives do matter more (Netflix exclusivity for a while, Halo, Gears, Fable) and PS3 add-ons like the DVR don't exist and you have a much more level playing field.
I will admit that nationalism might come in to play, all other things equal between the two systems but the two systems are NOT equal in anyone's eyes and thus I don't think nationalism would come into play much.
