Based on the above, I propose to close this thread, because there was only one USSR. And to keep this thread closed until Alexey Punk provides a link to a source stating that there were no USSRs at all or that there were more than one (two, three or more).
In the meantime, I suggest creating a new thread where we could discuss what the Soviet Union actually was as:
a) a socio-economic entity (please excuse the term);
b) a political entity, etc.