I know a decent amount about Latin America, and a small amount about Sub-Saharan Africa, and almost nothing about Eastern Europe, so take this with an appropriate amount of salt, but....
I really don't understand or accept the Putin >> Obama narrative on Ukraine.
As I see it, Putin used to, de facto, have the whole Ukraine. But he and his stooge pushed things too far. Amazing and brave Ukrainians rose up, stood up, and got out from under Putin's thumb. Now as a blustery, face-saving measure, he's got "secret" troops in the Crimean Peninsula and there may be a referendum there about joining Russia.
People, the loser here is..... PUTIN!
Putin, people, not Obama. Obama and the US are fairly close to irrelevant.
Putin is going from de facto control of the whole country with little external costs to him of exercising such control, to perhaps de jure control of the Crimea with significant external costs to him of exercising such control.
That is not how geniuses do things my friends.