USSR was a big space with lots of people and resources so it is a nonsense to compare it with Cuba and it is normal to not have free economic exchange with a state which is openly proclaiming that it will destroy you.How about the economic warfare waged on the USSR?
The information belongs in this link belongs in this discussion, but it can not be copied and pasted. The west waged economic warfare against the USSR as it waged economic warfare against Cuba. No economy can flourish when it faces such economic warfare.
From Blockade to Trade: Allied Economic Warfare Against Soviet Russia, June 1919 to January 1920 on JSTOR