The parameters of this discussion were 1st Germany and Poland invade Russia, then the reverse, then they liberate Ukraine and now we have NATO vs Russia.

 

Before anyone comments consider the odds of Russia using nuclear weapons to defend Kaliningrad, much less what they might do in response to the 80% ethnic Russia population being "annihilated".  Then the odds of Russian use of nuclear weapons in response to conventional attack by NATO forces within Russian territory.

 

After one considers this for a bit one might then consider whether NATO would vote to go to war with Russia in response to Russia militarily occupying Ukraine.  It's merely my opinion but I would bet against NATO doing so.

 

The question is not whether NATO could conventionally militarily liberate the Ukraine from Russia.  The question is whether at the political level Russia would allow that conflict to stay conventional and most importantly what do the nations of NATO believe.

 

Lastly, just like the Cuban Missile Crisis it's important to know with certainty whether there are tactical nuclear weapons in Kaliningrad and what are the orders of the local commanders.  NATO is not going to invade much less ever destroy Kaliningrad in my opinion.  YMMV.