Okay, this is an interesting point, but I'm not really convinced. If Our Lady appeared when Russia was called the USSR, and requested that "Russia" be consecrated to her Immaculate Heart, and requested that that be done immediately, then she obviously knew the place was called USSR, and yet referred to it as Russia. So she obviously wanted Russia to be consecrated to her Immaculate Heart. The pope could have just consecrated Russia, and if someone objected that Russia didn't exist, he could have said, "Well, tell that to Our Lady."
Besides, if Russia didn't exist in that time period, then neither did the "peoples of Russia".
It doesn't really make sense to say that Heaven would tell mankind to do something that is impossible, knowing that the command will be disobeyed anyway. God doesn't command anything impossible.
What I meant, at least in my comment, was that temporally there was no "Russia", albeit God knows the bounds of that nation regardless, so this was a defect on behalf of these Popes and not Our Lady.