well, "usually" the geographic divide is placed either at the Ural mountains, and southward through the caspian sea. (which cuts off the western third of russian, more or less.)
That said, if you go with geological distinctions, there's only one tectonic plate covering eurasia. So it's important to note that what it really comes down to is an arbitrary cultural distinction; basically a "are they more east or more west". and that's above my paygrade.
I'm just here to mock them any way I can.
It should also be noted, that part of the reason for the line in Princess Bride is what happened to the germans picking fights with the soviets- which was definitely a military blunder of epic proportions.
The ostensible reason for the German invasion in ww2 was because they needed a source of oil to continue the war effort. which, the military staff wanted to invade the middle east, Iran, Iraq. Palestine, etc. I forget what they were called at the time. the middle east was largely equipped and armed with cast offs from ww1; that were obsolete before that war had even ended.
But Hitler insisted, instead, of going into Siberia mostly because he absolutely loathed and despised Stalin. Which, there's no reason to believe that the Germans couldn't have steam rolled the middle eastern states. the question I have is how the occupation would have gone over. history says that holding Arab states is not an easy proposition. Suffice it to say that ww2 was likely to have been far more protracted than it was.