You are incorrect. World Wars I and II were not caused by the split of Central or Eastern Europe but due to nationalities being across imperial boundaries.
This case is completely different -- to the east of the Dnieper river are people who feel part of Russia, who speak Russian not any Ukrainian dialect.
There will be in fact the opposite of what you stated - since a Western Ukraine would be overwhelmingly "Ukrainian", it would be better for relations between East and West.
Sounds like you are suddenly agreeing with me, perhaps inadvertently. The core of that is that empires caused both of those world wars. And we have two nascent empires on the scene in Europe right now. The only way to peace in Europe is the absence of those empires, but no external force is trying to make them go away right now.
World Wars I and II were not caused by the split of Central or Eastern Europe but due to nationalities being across imperial boundaries
Please learn your history. That's carving up Eastern Europe again, and that always led to war.
There will be in fact the opposite of what you stated - since a Western Ukraine would be overwhelmingly "Ukrainian", it would be better for relations between East and West