What is Britain had not entered WWII

[ReluctantSamurai]

The second problem is that the whole plans true intention was to send some token aid to Finland but to occupy the northern part of Norway and Sweden to prevent the sale of iron from there to Germany.

Yep, but it would certainly do a lot to push Germany and the USSR even closer than the Ribbentrop-Molotov pact

So war against the USSR would have been a justified war with a casus belli

Japan had always known the real fight for dominance in the PTO would come against the US. Why else build the navy they did? After Khalkin Gol, only extreme hardliners like General Tanaka (commander in Chief of the Eastern District Army), and other high-ranking officers in the Kwantung Army who wished to further their own careers wanted to continue the struggle with the USSR. But the beat-down administered by Soviet tanks and artillery, and the subsequent horrendous casualty list, was sobering to many others who had wanted war with the USSR. Japan was simply not equipped to take on the Soviets. They had neither the armor, the mechanization, nor the artillery to make any real headway. As stated earlier, in the Japanese AGS own assessment, they felt that a limited breakthrough could be managed in Mongolia, but that they didn't have the rapid mobility required to exploit such a breach of Soviet positions.

An attack north would have required the withdrawal of large numbers of troops from China to be inserted into Manchuria, which the generals prosecuting the war in China opposed. In any case, what's the objective? Oil is of paramount importance, and there's none to be had (at that time) in either Mongolia or Siberia. The DEI is weakly defended, and the IJN can now do what Japan had intended it to do...conquer the Pacific.

And that means war with Britain. Even if fantasy prevails in Europe, what happens when the Brits have to go to war with Germany's ally?