Crazy idea!! Well consider Hitler's position. Japan had failed to attack the USSR in June 1941 in conjunction with the Germans and although this was not strictly contrary to the Pact signed between the two countries, it was certainly against the spirit of the agreement. If I were Hitler I would not be too pleased and would question the value of the Japanese in my schemes. So when Japan attacked a white nation - the USA, I would muddy the water by declaring war on Japan. As this would cost me nothing, i would expect the US concentrate upon the Pacific, might even get some gratitude from the Isolationists and would make FDR's policy of supporting the British that more difficult.
???? Hitler made no effort to involve the Japanese in attacking the Soviet Union, even as Barbarossa was being planned months ahead of time. To the contrary, Hitler and Ribbentrop were encouraging attacks on British holdings in the Pacific - and not any direct attacks against the Soviet Union. Further, it was at this time, that Hitler pledged his support to Japan for an attack on the United States. So, it is a "given" that Hitler neither wanted nor thought he needed Japanese "help" in defeating the Soviet Union...What he needed was a "distraction" for his invasion. So, why would Hitler be upset with the Japanese, when they did just what he wanted?
What good would it do? The German's had no way to attack Japan realistically, and the Combined Fleet wasn't going to sail around the horn to get at Germany.
I would think the point would be to make it much harder for the US to declare war on Germany. Not that he really would expect to take any real action vs Japan.