What do you think they are doing now?
http://www.bbc.com/news/world-us-canada-35476180
http://www.nytimes.com/2016/02/03/world/europe/eastern-europe-us-military.html
No really knows what Putin as in plans for other nations, but the Russian military has violated airspace, kidnapped an Estonia that was part of the military in their own country, used threatening language, I think used naval ships as posturing, military buildup on borders of other countries, constantly lied about Ukraine, etc. It really doesn't matter though, what matters is that many people feel threatened. Russia isn't going to invaded now because the US as a military presence there, but they have conducted some form of tactics that isn't conventional warfare
http://www.bbc.com/news/world-europe-32741688
https://www.youtube.com/watch?v=Xd3dM2IuMc8.
But none of that helps Ukraine or the people caught in this pointlessly destructive war.
I understand that now the US and its allies will implement all of these actions in reaction to Ukraine, but that just underscores how little they're actually doing to help end the violence that's happening right now, or to mollify Russia's concerns about its own security.
As you point out, no one knows what Putin will do. It's the $64,000 question. But the list of charges as it were against Putin is extremely minor in the grand scheme of things.
The US has spent 15 years believing that the risks of doing something, anything, weigh less than the risks of doing nothing. The US has interpreted its adversaries' actions in the worst possible light, and always as some first step towards larger and more nefarious goals. The US has brought about its own worst nightmares in an effort to head them off.
This is the core problem with Hillary. She's extremely intelligent and knowledgeable. But she buys into all of these assumptions about Iran and Russia and whoever else and those assumptions are very questionable. And the president does it a lot too to be fair. And Sanders as well. But less so than Clinton, I think (see his answer tonight on Iran).
Violations of airspace. Kidnappings in the Baltics. This is not exactly the makings of a new Soviet empire. That's not to say that these aren't problems. But let's keep them in perspective, and understand both the limitations of Western responses to Russia as well as the fact that Russia may itself feel threatened, rightly or wrongly, by the Western powers.
I think the US should strive for good relations with Russia. To the extent it can, it should be pushing for an end to the war in Ukraine in order to stave off further loss of life. Ukraine's loss of territorial integrity, I'm sorry, it's not that critical. If one believes it portends further depredations, then it might make sense to oppose Russia on this issue.
But that seems to me to be nothing but one of those suspicious assumptions that always comes down in favor of assuming the absolute worst intentions in an opponent with very little evidence backing it up.