@Gharen:
Here is a link to Larry Harris Game Design website where a person posted asking the exact same questions as the original poster of this forum post and took a shot at answering his own questions. Krieghund replied by saying the poster was correct in assuming that at the moment Japan declares war on any of the Allied players, all units on the board are instantly hostile and don’t wait until each subsequent factions turn to declare war on Japan to attack.
http://www.harrisgamedesign.com/phpBB3/viewtopic.php?f=36&t=2152&hilit=Declaration+of+war
That question was asked and answered prior to the release of the official errata. It was based on the wording in the book, which has been replaced.
The replaced wording was a big improvement, but a few details were over looked. Which may have resulted in a few unintended consequences.
It’s possible to dig up past forum posts by Krieghund that are contrary to the current rules. So, they aren’t 100% right.