After effects of Nuclear attack on New York

I am curious what others on this forum think would happen should a terrorist actually nuke New York, (for example). What would the after effects be to our nation and the world? Firstly, What would the first 24 hours be like? How would we respond? Secondly, how adversely would this attack affect the US economy? For this speculation I think we should assume that we do not know who did the bomb, no one is taking responsibility for it, and that it was a small yield device.

If this has already been done, I apologize.

Personally I fear that just one bomb could cripple the nation. What a time for another nation to take advantage of us at our weakest also!

I would love to hear all your thoughts on this. Thanks!