Eh?
Conclusive proof? About something from Nostradamus?
Please.
I certainly realize that N's writings were very vague. I'm not even saying that this quote is a perfect match for the situation.
I do, however, see some similarities between this writing and the events of yesterday.
City of God? NYC the largest, and arguably the most important, city in the greatest (note: MHO; I won't respond to attacks on same), most powerful country on the planet. A loose interpretation of a vagur writing could interpret NYC as the City of God, in that sense. Certainly it might not be the City of God in the sense of how you perceive God, but that's your interpretation, and up to you personally.
-YendorMike
"The problems of the world cannot possibly be solved by the skeptics or the cynics whose horizons are limited by the obvious realities. We need people who dream of things that never were." - John F. Kennedy