By Putin? Yes, we can agree he's handling it poorly.
I don't think that Obama has done anything as bad as Putin has these last few months especially.
Even if we stipulate, for sake of argument, that Russia is entitled to a "sphere of influence", we do not agree that Russia has the right to invade and annex its neighbors.
The principle that national borders cannot be changed unilaterally is a pretty big deal. A very big deal. Do we want India and China marching on each other to take land that is "historically theirs" or "in their sphere of influence" or ....? You're aware of what's going on in the South China Sea now, right?
Obama has said multiple times, and demonstrated that he believes, that the Ukrainian problem is not a military problem. He's also said, categorically, that an attack on a NATO member is an attack on all. His hands are tied by the NATO treaty even if he didn't personally believe that war was a good idea. The Constitution saying that it and treaties are the supreme law of the land and all that.
Ukraine is in a bad spot for a lot of reasons. We're not going to go to war over it (even though we promised to protect its territorial integrity after they gave up their nukes). But we cannot, and will not, just sit back and say, "Oh well, Putin wants his sphere of influence, so that's the way the cookie crumbles." Putin is going to pay an economic and political price for his actions.
I suspect the way out is a weaker central government in Ukraine and an understanding (maybe unwritten) that Ukraine will not request NATO membership for X generations. I can't get a read on EU membership or not - maybe Putin will let that go in exchange for the no-NATO thing. Hard to tell.
Putin's playing with fire, though. Sabre-rattling only goes so far and doesn't make economic partners very happy...
(While I'm sure it's tempting to bring up Iraq - 1) we didn't carve it up, 2) we left, 3) subsequent administration has said the invasion was a mistake. Putin's greater-Russia actions are making it very difficult for him to back down (and harder still for anyone following him). I don't think Iraq applies here, and we know the arguments.)
I don't think we'd invade Puerto Rico if it were independent and wanted to join EU. YMMV. :-p
FWIW.
Cheers,
Scott.