One word. Miscalculation.
It's what has started about every major conflict in human history. One wrong move in this one could be the last in the series. For anyone who doubts me, I'll gave the same reading recommendation President Kennedy gave his advisors during the Cuban Missile Crisis -
The Guns of August by Barbara Tuchman... it's about how miscalculation lead to the First World War.
Fair enough and I don't disagree that the
potential exists for the situation to become very ugly. That said, my position on this and the reason I disagree with the OP and his 'changing world order' argumentation is that I would posit that the world order has
already changed, and Russia does not factor into it so significantly. The actual, new world order is China and its alliances/partners
competing against the United States and its alliances/partners. I emphasize the 'competition' because at the moment and for the foreseeable future, it is about competition, not conflict, much less the destructive kind of conflict that makes competition irrelevant.
I truly believe that given where we are, neither the United States nor China want an open and escalating war. The United States absolutely has enough weight to pull NATO back from the edge. And likewise I believe--and perhaps I'm the only one but it's my position--that China has similar influence on Russia from a practical perspective. If matters start to escalate, China will intervene, and without its safety net, Putin does not last very long in power.
So, I agree there's a risk that this becomes a flash point. If it becomes one then the OP may be considered a prophet of the time and I will have been proven terribly wrong. But for now, I think odds are that it doesn't go there, and this conflict falls somewhere just above the California summertime wildfires on the list of threats to the United States in the past 20 years.
And yeah, that isn't to diminish the fact that this really, really sucks for Ukraine.
I don't disagree with the OP that it's great that Biden is in the Oval Office instead of Trump. What a cluster that would be.