This is what really happened:
Ukraine and Russia were allies with trade agreements and military access.
Ukraine got an event and took the Russian option instead of the EU option.
As a result Ukraines legitimacy dropped which caused pretender rebels to spawn.
The Pretender rebels occupied most of Ukrainian thus they could appoint a new leader and (in this case) government type.
Ukraine is no longer occupied by rebels but has -3 stability.
Russian nationalists spawn as a result and occupy Crimea.
Ukraine has new national modifiers, +1.0 legitimacy per year and +10% trade/production efficiency.
Alliance with Russia is broken, relations drop.
Crimea declares independence ... very quickly.
Ukraine makes a guarantee on Crimea to protect their core.
Russia makes a DoW on Crimea, using a claim CB which causes Russia to take an AE hit.
Ukraine and Russia are now at war.
NATO, an alliance that includes mostly Europe and Nth America warns Russia, and allies Ukraine.
Ukraine calls to arms the NATO leader USA. USA for the moment ignores the call to arms message.
What happens next? Probably:
Russia annexes Crimea, takes AE hit.
Russia offers peace demands: Ukraine revokes cores on Crimea, peace.
Ukraine with no money, a very small army and limited support from NATO (USA has too many loans and high WE from Afghanistan, most of Europe do not want to embargo Russia) accepts the peace offer.
War is over (call to arms message to USA is cancelled).
Russia gets +5 prestige and +50 AE (UN modifier for late games).
Sochi building disappears (one of the requirements are, you must have low AE).
Ukraine joins NATO coalition.
On a serious note this isn't funny, people have died in the Ukraine riots and we are all lucky war was never really started.