The Soviets, unlike the Nazi scum that we annihilated, never annexed anything. If you have any factual proof I'd like to look at it, I'm confident because it doesn't exist in this world, unlike the fact that we liberated half the Europe and spanked fascists that you backed.
I don't say that you had to do it but if you have a brain, it is pretty obvious, the scale of the problem and the reward that you would receive, pretty much shouts to anyone with IQ higher than 10 that it's the best deal ever. You contribute to the victory against Hitler Germany, you receive more territory in exchange and you gain good relations with the USSR. The dumbest thing was to decline it, which you actually did. Sided with the Nazism and shamefully lost.
You started that war and you lost it. It's a big, big shame and those who study history, smirk with a grin on this moment.