I see you weren’t listening. There is no American conservatism in countenancing the retread of the breakup of Eastern Europe between “east” and “west”—acts that led to two prior World Wars. The pattern is so blatant, even Captain Obvious is saying nothing about it because he feels he shouldn’t have to.
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.