I know its a stereotype but is it true that our hard modes are the Japanese players easy mode?
The Japanese pool of players are a different breed than the US pool. That doesn't mean that the Japanese are an uber-elite while the Americans have the skill of a 5 year old. To me, it just seems to be a part of the way the culture and in which the Japanese were nurtured.
Back in the late 80's/early 90's, this sort of thing did happen where the US part of the company didn't want to bring a game over or toned the difficulty down because they thought it would be too hard for our feeble minds. Now a days, I don't think this happens any more.
Megaman 2 is a case where they offered two options of difficulty in the US release. The hard difficulty in the US release is the only difficulty in the Japanese release.
Super Mario Bros 2 was never brought over to the US because, again, they thought it would be too hard. Granted, this time their expectations were right, because that game is much harder than the first one. So, they decided to wrap Doki Doki Panic in another wrapping paper and called it SMB2. The actual SMB2 was released later in the All-Stars collection entitled SMB: The Lost Levels. (Also, the American version of SMB2 was released in Japan as SMB USA)
Another case is Final Fantasy IV, or as it was called II back then. They changed a lot of things, again, thinking that so many things in the game would over-complicated the game. Funny thing is, Square actually released an easy type version that was easier than the US release months later. I believe this was because RPGs were just starting to get mainstream, and also the original version itself can be challenging.