Instead of regional discussion threads, how about a culture subforum? We can have Japan be a fixed category, because, well, it's Japan, the mother of all things great. Then we can each individually create topics relating to our ethnicity, culture differences, vacations in foreign nations, customs in each nation, hotspots of particular nations, etc. etc. I personally vouch for this.
The problem of a regional subforum is that what's there to discuss other than the fact we come from the same region and share similar interests? A culture forum instead would encompass that and include more topics of interest and easier things to discuss. Most importantly, this allows everyone a chance to view and experience another person's culture.