Russia has already taken the Crimea. Russia is likely to annex all of Eastern Ukraine, and will definitely work hard to re-install a puppet government in Kiev.
If Americans want to stop Russian aggression, we need to get off our asses and start doing it in earnest. If we want to avoid conflict with Russia, we need to back off. Probably the worst thing we could do is make a half-hearted attempt to help Ukrainians provoke a hot war with Russia that will simply be a bloodbath for them.
Really, if we wanted to keep Russia out of the Ukraine, militarily, we should have put our foot down on the Russian incursion into Georgia. Chechnya was a bit tricker, because Chechnya was legally a part of the Russian Federation, not a recognized independent nation.
It's a mistake to think of Vladimir Putin in terms of presidency. He's first and foremost an intelligence officer who is a member of an economic and political elite that rules Russia with a festively decorated iron fist.
"Russia" doesn't just DO things. Russia does things for very specific reasons, and with long-range planning. This fact is easy to miss, given the remarkably poor long-range planning apparent in the collapse of the Soviet Union. But consider for a moment the fact that the Soviet elite became the post-soviet Russian elite and got filthy rich, and perhaps this long-range planning is a bit clearer.
What does Putin's Russia want? I'd wager they want to keep their top-down power structure, complete their transition to a functioning capitalist market system, and regain control over their immediate neighbors (and those neighbors' economic assets).
What can the West do to help ensure that Putin's vision for Russian succeeds? Well, I'd say that providing Putin with a clear external enemy would be to his liking. Maybe even better if we hurt the common man in Russia with economic sanctions. This kind of thing would tend to consolidate Putin's hold on the hearts and minds of common Russians. We could provide Putin with a scapegoat for Russian problems, distracting from the fact the Russia's problems are RUSSIA'S problems, and those who are most to blame for them are Russia's elite.
And what can Putin do for Western Elites? Might be worth asking ourselves that question before we break open all our piggy banks to pay for new weapons systems. Russia may even hope to destabilize the US by provoking us into military over-expenditure. That's a big part of what we did to hasten the collapse of the Soviet Union, and we're only just beginning to dial back the crippling military budget associated with the "War on Terror." Wouldn't it be nice to send kids to college? Invest in new industries? Modernize US infrastructure? Employ marginalized youth in civic works projects?
Whatever we do, we should really think it through first -- because I guarantee that Russian intelligence and other power brokers on the world stage have a game plan in motion, and it probably includes a highly sophisticated analysis of what the US is likely to do IF WE DON'T THINK THINGS THROUGH.