[Sherman Logan]

You are quite correct. It has been pointed out that Hitler had no treaty or other requirement to declare war on USA. He just decided, all on his own, to do so.

[Axenolith]

ARTICLE 3. Japan, Germany, and Italy agree to cooperate in their efforts on aforesaid lines. They further undertake to assist one another with all political, economic and military means if one of the Contracting Powers is attacked by a Power at present not involved in the European War or in the Japanese-Chinese conflict.

At the time, the U.S. not having initiated the attack on Japan probably wasn't making the rounds in Berlin.

[ExGeeEye]

Thus falling into FDR’s clever trap. (nodding sagaciously)

[ExGeeEye]

I have taken note of how assiduously Hitler adhered to his treaty obligations. Two in particular might have prevented full-scale war (Versailles Treaty, and German–Soviet Non-aggression Pact) had it not been for the wily FDR's machinations, so well was Hitler observing their provisions.