I kinda agree with some of the assumptions here...
1. I agree that no matter what USA would have ended up in the war against Germany eventually anyway.
2. Due to USA entering war, Germany was the bigger threat, requiring about 66% of US resources (historically), so USA would crush Japan quite fast and easily.
Due to this I actually think its in Germany's best interest to declare war on USA as soon as Japan declares war on USA, otherwise the troops that USSR and UK have stationed in Siberia/India/Phillipines/ etc can be freed up to fight Germany much quicker and thus lose the war much quicker for Germany.
It also means if its anything like HOI3, that Great Britain will never surrender because you could never control enough victory points in Europe and Africa alone, you need Japan to take out victory nodes. This doesn't really matter though because from what I remember when a member surrenders in HOI3, the remaining naval ships are transferred to the next leader, which would be USA, the only thing that gets killed is army units and air force.
Edit: This was my strategy in HOI3 and HOI2, to draw as much naval units into the atlantic sinking as many of them as possible, and continuing the massive submarine blockade of Great Britain. This frees Japans Navy quite a lot.