I'm sure every major exchange has contingency plans to operate out of a backup location. I'm not aware of any single point of failure in banking, oil, or cargo, and if there were, mundane threats like weather would far outweigh terrorism anyway.
If the NYSE building were bombed on an operating day, it would absolutely have dramatic financial repercussions, and that market would absolutely be crippled. Would some simile reappear? Of course it would, just as government would reappear if a full capital building were attacked. But the impact would be major and it would be felt.