From what i've seen on my travels the only countries that require a ground at every outlet and on every plug wheather it's class 1 or class 2 it has to have a 3rd pin even if not connected simply to fit into a socket use the UK standard outlet (BS1363)
I found grounding in most normal buildings in the US not all that great.
France/Germany are fine in new buildings lots of ungrounded outlets in older french bedrooms
As for japan, you could be looking at older outlets.. or they may require grounding on specific outlets only.. e.g. for heating, washing machines etc. there may be a strict requirment for double insulated appliences.
