One thing I've noticed that is different between the US version of the Fuji 200/400 films from the ones from other countries is the color temperature. I don't know if this is a purposeful act on Fujifilm's part to adjust for that part of the world's general sky/lighting conditions or of it's a variation purely of coincidence... perhaps a manufacturing variance from batch to batch. It's difficult to tell unless it's a stark contrast in color or grain.
I know that when I shoot the Fujifilm 200, I like to warm it up just a bit with a very light warming filter if I am shooting somewhere that the blue cool tones might be overwhelming. But, since it's so cheap, I usually shoot it for things that aren't as important, perfection/color wise.
If shipping some to you in Japan was not so expensive, I'd be more then happy to send you some of the US Fujifilms to try. Most places locally like Walmart here have the 200/400/800 usually. I only get them online unless they are on sale locally. I've never seen any 1600 of any kind from Fujifilm online or here locally so I can't speak to it's qualities. If I want 1600, I just push it post shooting and deal with the grain.