The third and fourth points are just hand-wavey aren't they? 'Russia would have invaded Ukraine anyways' is rich coming from them - RWN also though Russia wasn't going to invade at all back in the day. Moreover, what sort of counter-factual is 'the empire just doesn't care all that much about North Korea'? Are we going to say that about every country between Cuba and Iran until the US actually goes ahead and escalates its wars against them?

If Ukraine losing a fourth of its territory isn't existential enough to raise the risk of nuclear war then, well, at that point you might as well argue that nukes are useless actually and nobody is ever gonna fire one. I for one thing it is much more convincing to argue that Israel - backed by the US - did not feel existentially threatened by Iran and that neither did India or Pakistan in their small war.