An ASB and the Soviet invasion of Manchuria

   A lot will depend on how things develop.  Some points that would come to mind.

a)  There are going to be repercussions inside the USSR.  I wouldn't like to be the person [corpse?] who has to go to Stalin and try to explain to him that all those troops and their equipment are now thousands of miles and weeks away from where they need to be to launch the planned attack.  There are probably going to be a number of former officers finding new employment in the gulags.  Its also going to strain relations with the US especially as their not going to believe what's happened and hence the Soviets are thought to be breaching their agreement to join the war against the Japanese.

b)  Of course with so many people moved magically along with all the people who will see them disappear/arrive this could have longer terms impacts.  Some might see it as some sort of divine intervention opposing the war against Japan, or possibly more dangerously as a sign of displease against Stalin.  Not expecting, with the power he has that he will be removed but there are going to be amazement and uncertainty at this event and what it might mean.

c)  A lot will depend on how long it takes for Japan to be forced to surrender and whether the Soviets are able to play any role in it.  However its likely that Korea could end up under western control and Mao not getting those weapons.  Nor control of the industrial areas in Manchuria and the relatively easy further supplies to him from the Soviets via Manchuria.  It might not change the final result depending on how weakened the KMT are by this time but at the very least its going to be a longer and bloodier conflict and China might stay under KMT rule.  [Or possibly most of it but still have significant areas under CCP rule possibly directly supported by the Soviets].  Either way that's going to be a big butterfly effect both for China and the wider world.

d)  If the US has to invade Japan its going to be very bloody, especially for the Japanese.  Which is likely, along with probably no Korean war, to reduce the chances of a Japanese economic revival as OTL.  [Because of even more destruction, deep mistrust between the US and Japan, the lack of demand for products for a war in Korea that helped restore parts of the Japanese economy].  Even more so if one result of this invasion is that the US decide to remove the emperor, whether in person or the office as a whole.

  Assuming this - which requires really a Japanese surrender before soviet forces arrive back in Siberia so isn't totally certain given how deranged much of the Japanese leadership was - it could simply tempt him to do a direct attack on Korea rather than sending 'volunteers' to help NK as OTL.  Depends on how things go with the ending of the war and how the cold war develops.  Its possible that a united Korea under western control will be seen as too much of a threat both to Mao and Stalin - with Vladivostok only just over the border.  At the very worst you could end up with clashes that end in WWIII. 

  Not saying that's certain but I wouldn't rely on a unified pro-western Korea being a check on communist power.  Mao was so barking mad much of the time he ruled China that its difficult to see what way he might jump.  Its better if he never comes to power, which is more likely if a Japanese surrender results in Korea - as well as Japan - coming under western occupation and Mao loses the civil war as a result.  In that case the spark point is likely to be tension between Russia and China with the latter getting US support.  In that case, unless everything goes to pot, Korea would be a relatively small backwater that might as a result develop into a fairly liberal and advanced state as S Korea has OTL.

  If that happened Stalin keeps the western powers happy by complying with his commitment to join the war against Japan.  However it could lead to problems on the Manchuria front.  Doubt the Japanese would do much attacking given how thinly stretched they were and the Soviets had some other forces there.

  The other issue is while Stalin is cursing about what's happened and probably some officials and commanders are being shot or visiting the gulag how much would anybody outside the USSR actually know about this.  Given how wild the event is and Stalin's customary paranoia and secrecy he probably would be reluctant to tell any foreigners about it so the western powers might think he's only made a minimal effort.  Although I don't know if any western representatives were with the forces affected but probably not.