I'll bite:
The U.S. government deliberately provoked the attack on Pearl Harbour through diplomacy and/or fleet redeployment, and it was not by chance that the carriers of the U.S. Pacific Fleet weren't at port when the attack happened.
Very confident. (90-95%)
By the way, the reason I assume I am personally more rational about this than the LW average is that there are lots of US Americans around here, and I have sufficient evidence to believe that people tend to become less rational if a topic centrally involves a country they are emotionally involved with or whose educational system they went through.
Upvoted, not for the assertion, but for the confidence level (I would give it 25-75%)
I was very interested in the discussions and opinions that grew out of the last time this was played, but find digging through 800+ comments for a new game to start on the same thread annoying. I also don't want this game ruined by a potential sock puppet (whom ever it may be). So here's a non-sockpuppetiered Irrationality Game, if there's still interest. If there isn't, downvote to oblivion!
The original rules:
Enjoy!