North Korea's fate was decided by the Soviets just as much as South Korea's was by the US. There were even Soviet pilots flying in the North Korean air force in the Korean War. The Soviets didn't have the ironclad control over North Korea that they had over Eastern Europe, but they certainly weren't any less involved than the US was in the South.
Say what you will about the US, but I think the results of a Stalinist / Maoist mashup speaks for itself. It is and was pretty obvious who the agressor was in Korea -- the Soviet tanks rolled into North Korea weeks before the Japanese surrender specifically to grab Korean territory. The Northern attack on the south was very clearly a land grab.
