To suggest that US models are in English and that, therefore, the Japanese models should be in Japanese is incorrect on so many levels that I hardly no where to start.
1. I believe that US models will offer mutliple languages, just as the DMV or just about any other place does.
2. Written Japanese is based in Kanji. Do you know what that is? It means that if you don't know the sound, you can't look it up. Each kanji can have from 1 to 120 different sounds attached to it. Does this sound reasonable to expect expats (read: people from anywhere in the world) to be able to do?
3. The software is already localized to different languages and the choice not to apply thTose localizations is not based on resources or logistics. It is based on race and market protection.
4. The software not being compatible excuse is so lame that it doesn't even bear recognition. Let me guess, the routers have the same name/model number and the same functions, but the software is incompatible? Do you even listen to yourself? Just about the only thing different between the WZR-HP-300H J-version and the I-merican model is that the language option has been removed. So what are you talking about, and are you just trying to yank our chains?
I know of what I speak as I have lived in Japan for the past fifteen years. How about you, or are you just talking because you have lips. If you wish to educate yourself prior to making another comment on the subject, try checking up on the "keiretsu" in Japan and how they conduct business. If you can't find it, ask me, and I will show you how to write it in Japanese so that you can try looking for it over here. Alternatively, just try stepping out of I-merica for a day and then come back and share your wisdom with us.
Buffalo doesn't deserve the business and you don't deserve a job--in my own personal humble opinion, of course.