It's a bit different though because Russia and Ukraine are so close. It's a bit as if the US would attack Canada.
- Pro-China forces got into power in Canada after unconstitutional coup.
- China has started to actively train and supply Canadian military. Of course, solely for protecting Canadian sovereignty. /s
- Anti-imperialistic (read anti-US) propaganda run rampant in the country.
- Pro-US parties and media got either closed or pressured to the point of non-relevance.
- The Canadian govement has declared that it wants close economic ties with China and to join its military bloc.
- English was pressured in favor of French to protect Canadian culture.
If you think it's too unrealistic, just remember the Cuban missile crisis.
And because of the aggressor's response (annexation, mercenaries, un-uniformed troops) Ukraine themselves sought security guarantees from other partners.