The Japanese strategy at the time was built on the idea that they would win a decisive navel battle which would cause the United States to just decide it wasn't worth it and they'd quit. Even after Pearl Harbor they were trying to accomplish this through 1942 - 1943 when it finally dawned on the few reasonable individuals in leadership that they were going to lose.

The Japanese really had no intention of working with the Germans to accomplish much of anything and didn't really concern themselves with what was happening in Europe. The United States didn't use military force in Europe until Germany declared war on them. Some would even wonder if Germany hadn't declared war if the USA would have ever sent troops over. Even before Stalingrad, the Japanese were under the correct assumption that the Germans were not going to find success against the Russians. They were very resistant to offering any military support that might bring the Soviets into the conflict.

The Japanese simply made a wrong assumption about the military dedication of the United States once sovereign territory had been attacked. There were more than a few reasonable individuals in the Japanese government who tried desperately to dissuade Hideki Tōjō's hawkish desire to neutralize American holdings. The reality of the situation is that if the Japanese had not attacked any US holdings in the Pacific, the United States probably wouldn't have been drawn into al-out war and things would have gone better for the Japanese.