The Ukraine is an artificial country created by the communists. Prior to the breakup of the Soviet Union in 1991, it was never an independent country. It was always, essentially, part of the same country as Russia. It was effectively first created as a separate legal entity after the Russian revolution in 1917 when the communists created for their own political purposes.
Furthermore, Crimea has been part of Russia for hundreds of years from the time of Catherine. It was only transferred on paper, since it made virtually no legal difference, from Russia to Ukraine in the 1970s by the Ukrainian dictator of the USSR, Krushekov.
And in 2014 Obama and Hillary supported and assisted the violent coup d’etat against the democratically elected President of Ukraine, replacing him with an anti-Russian government.
America and NATO have no interest in protecting the Ukrainian government.