The specs of the Japan ext. HD must be ready for the OS of your laptop and be a match of the port you're using. Unless, there is some buried h/w firmware of regional issue, then it should work. You do need to format and/or prepare the ext. HD to be used as it maybe not ready for English use.
You did bring these issues up when you brought it or similar? Plus, how is it powered?
Just wondering if anyone can tell me why a Japanese external hard drive can't be used with a North American laptop. I am currently living in Japan using my laptop from Canada and would really like to find an external hard drive to use. Any help about if there is anything I can do to make the two compatible would be really appreciated.