Gee if fractures within a country make it eligible for Russian invasion then I guess we ought to get prepared
Imagine an independent Texas (many in FR do). Imagine politicians trying to radicalize a split between Hispanic and White / Spanish-speaking and English
Imagine China, in alliance with Mexico or other nations, feeding arms into this political and cultural split, supporting one party over another, or arranging coups. Imaging them forming a military alliance which would take foreign troops to Oklahoma borders. Ya' know - "supporting democracy, and stuff"
You'll start to understand Ukraine's situation.
And yes, in such a case, you had better be prepared.