As for lowering the threshold, I’d say that was successfully done by western politicians a decade ago when it was suggested to be okay to bomb Iranian nuclear facilities. Holy Fukishima! this was treated like a perfectly reasonable action. Yet another threshold lowerer, is the naked aggression and disregard for international law that the US and NATO has shown. We’ve attacked and invaded twice as many countries as Hitler did prior to September 1939. And Hitler’s aggressions were mostly bloodless, while all ours are very bloody! No reason for the Russians to ever feel threatened if America wasn’t trying an annual regime change on whatever country Washington doesn’t like. And they have made their dislike of Putin and Russia perfectly clear!