I will test it out once I recieve the chip. You can see from my flag that iam from the USA, so I will see what happens, and post it in my review soon.
If you want my opinion of this matter, I would say, yes, it will work, but Im not totally sure, so please dont quote me on it. The reason why I say yes, is because, well both US and JP formats on its bases, are NTSC. If you try playing a PAL game on either US or JP consoles, I suspect that the screen will be screwy, since both the Wii and the T.V. does not support the format. But in NTSC's case, It seems that both US, and JP both work on eachothers console, and their respective television sets. Plugs are the same, signals the same, every thing is pretty much the same except for the language, and the extra "J" at the end of the "NTSC".
Again, Iam not sure, but I assure you that I will test this out in my review, hopefully. I will have to try to find a "copy" of a NTSC-J Wii game, so if anyone would "lend" me a hand, then I will be more then happy to metion you on my video review of the Wiinja.