Most of WWII was a Euro-Centric war-— and you can see this in the various TV histories that for the most part ignore the Pacific theater.
FDR and his euro-socialist pals focused on Europe— because of the Brits. The Ribbentrop Molotov pact was broken by Hitler in June 1941. Pearl Harbor attack in Dec. 41. Stalin— who was a psychopath and could not see another one in hitler— was stranded— then to be our “ally” of sorts.
There is excellent info on the Jap ambassador to Berlin—and his close relations with Hitler on the subject of why no demand japs declare against the Sovs. The matters in the Ukraine, white russians came into the mix.
The whole thing makes sense when one realizes the level of penetration (the cambridge 5 et al in Brit govt. who all worked for the soviets). Agents in place steered the war effort to help soviets. Japs were already in Manchuria (Manchukuo) and on the soviet border. The Brits made sure the US entered the war-— many threads on this one now declassified story of the jap codes and purposeful deception of the Brits (who were, remember compromised by stalin).
To counteract this— the rewritten soviet “meme” is that FDR callously let the soviets slug it out vs. the Germans on the Eastern Front to save US lives. FDR being the genius and all, more likely... a patriot got between Dexter White and Hopkins et al. so they couldn’t push the Southern front invasion sites instead of Normandy. Patriots like the FBI maybe who knew White and Hopkins were bent.
No doubt that all of Britain, the Soviet Union and communists everywhere wanted the US to enter the war against the German juggernaut that threatened both Russia and Britain. No doubt Britain had cracked the Japanese code, knew that Pearl Harbor would be attacked, and withheld the information. The Soviets had penetrated the Roosevelt administration and used every overt and covert ruse to get the US involved against Germany. Still the Soviets feared a two front war. If the Japanese attacked, the Soviets would have been very hard pressed. They were probably astonished that Hitler declared war on the US and did not get a commitment from Japan to attack the Soviet Union.
The Japanese had had their asses handed to them by the Soviets (led by Zhukov) at Khalkhin Gol in 1939 and had just signed a peace treaty just two months before the Germans invaded the USSR. Plus they needed their resources for their drive into Southeast Asia, which had strategic benefits far beyond what invaded eastern Siberia would yield.