well, so you think, all parts and peoples of USSR were voluntarily part of USSR?
No, not all, though you will be surprised how many convinced communists were even in Lithuania, to pick one example (a fact which today's Lithuania hides).
And do you think the people in Europe are voluntarily a part of your undeclared, but very much existing, empire?
I was going to say that no country actually chose to join the USSR but perhaps I'm wrong.
Did any country voluntarily choose to join? Maybe Belarus?