I think your confusing two ideas here. (1) The military threat Russia poses to the USA/NATO/EU/UK/Ukraine and (2) the political threat Russia poses to them. I agree that since the fall of the USSR the USA/NATO etc never really felt threatened militarily by Russia, which is why they felt they could get away with their bullying gambit to encircle Russia. But the fact that Russia has now out maneuvered the USA/NATO, defeating them militarily in Ukraine and defeating them economically and diplomatically on the world stage, is very much an existential threat to NATO and more particularly, the American Empire.The USA's status has been severely weakened for all the world to see. Countries are rushing to join BRICS and welcoming de-dollarization and America's sabotage of the European economy and its continuing military occupation of most EU countries, is really pissing off the European population and has them questioning why they need to continue being part of NATO. That's why the USA/NATO is pushing the idea that Russia wont stop at Ukraine, So a defeat in Ukraine for NATO is a disaster. It tells the world that NATO is not in fact this great power that cant be defeated (a serious loss of prestige) AND it tells the Europeans that maybe NATO cant really protect them and that they need to start backing the Russia/China horse which is growing exponentially in economic and military power. No, when Stoltenberg said that losing this war is an existential threat to NATO he was being totally honest and he was absolutely right. That's why the USA/NATO is very dangerous now and IMO are far more likely to resort to nuclear weapons to save their empire slipping through their fingers.
