Sort of. Russia needed to annex Crimea prior to the Ukraine joining NATO, which was becoming more possible after the revolution in Ukraine. Russia didn't need to act prior because it isn't threatened if the Ukraine isn't looking towards joining NATO. Crimea is hugely important to Russia because of its port access, which is why Turkey is now becoming more important to Russia (If they have the Crimea ports, Turkey controls Mediterranean access). A parallel story for the Americans would be if China suddenly signed a military treaty with Panama, which means that they could presumably restrict sea access significantly.