“The Soviet tank forces in the Far East were mainly BT-5's and BT-7's. All available T34's were facing the Germans. And even during the Khalkin Gol conflict, Soviet tank losses were very high due to "banzai" tactics that took advantage of the BT's penchant to catch fire.” True, but the Japanese still lost the battle. The Russian improved their side, the Japanese not. The Russian did learned their lessons front 1941, Finish War and reacted in producing new tactics. The inferior (compared with Russian) American Tanks (Grant) were more than match for the Japanese Tanks.
Then, if we speak of a Japanese attack, as shown in Malaysia, their logistic was too weak. You might leave on the country in Monsoon Countries, Siberia would be more difficult. Then, what would be the profits, gains, in Japanese terms? As mentioned, Siberia wasn’t really exploited at the time (except Gulags). The Sun Empire needed immediate profit, things to loot and with immediate effect…
And it would have distract forces from where they were needed..

“The USA was looking for a cause”: Yes, the President did. But, without Germany declaring war, nothing he could have done. Roosevelt turned back the request for help for French Paul Reynaud in 1940, as he had no choice…