> Nor should they. <
If you mean that no power should step in and fight Russia over the Ukraine, then I must agree with you. But if you mean that Russia somehow deserves eastern Ukraine, then I must disagree. Unlike with the Crimea, even eastern Ukraine is heavily Ukrainian by nationality. Russia has no moral right to that land.
But as I’m sure you would agree, it’s all not worth the bones of a single American soldier (to paraphrase Bismarck).
“If you mean that no power should step in and fight Russia over the Ukraine”
Yes