It makes sense because Russia is currently facing the exact scenario I am describing.
What should they do? What would the US and UK do in Russia's current position?
Probably war. They have started wars for less.
And, BTW, NATO was created to fight the Soviet Union. Once the Soviet Union fell, NATO probably should have ceased to exist too and the West could have been friends with Russia, but instead it continued moving east towards Russia as an enemy (which it no longer should have been after the fall of the Soviet Union).
Okay, but expect conflict. Duh.
Russia expressed interest in joining NATO too, funnily enough, on multiple occasions, but could not. 🙄