Russia is not the Soviet Union. Containment was against communism. Containment of or attempted containment of normal great power behavior in a corner of eastern Europe has no , to me, compelling interest component for the US. If it is a problem for anyone it would be European countries. The return of the domino theory does not stir me. At most it may be of some interest to the US to provide enough material support through intermediaries to keep the Russians and Ukrainians fighting among themselves so that potential Russian-Polish conflict can be discouraged.
You are a very foolish person. Russia is an ally and supports every communist country on the planet. They are also supporters of our greatest enemies in the middle east, Iran and Syria. Russia is a totalitarian kleptocracy, probably the ultimate evolution of communism itself, just pure power and massive theft. To say otherwise marks you out as a fool. And do you not remember Georgia? What did conservatives say would happen then? "Ukraine will be next if the U.S. continues to be weak." That's what happened. Though I will add, that even if Russia was happy to only gobble up Ukraine, I would still call for our help-- because we must aid patriots and good people where ever they are.
Either way, containment is the only answer- or more violence shall rise up. Weakness will only drive them further and further, because they hate us, and want to rule the world.