I don't see a reason to delay elections if the attack is the day before. The Supervisor of Elections in each county/district/voting block should have a continuity of operations plan in place in case one or more polling sites is made unusable.
If the attack is on the day of, then I don't see why the election should be delayed for all the USA. Those polling areas effected by a terrorist attack can have their ballots cast the next day at alternative sites or by whatever means the Supervisor of Elections selected in their continuity of operations plan. I don't know about other areas, but I can tell you that in Florida, ever since Hurricane Andrew, all government agencies have had to have a continuity of ops plan.
As far as emotions...the US held elections during the Civil War, WWI, and WWII...pretty emotional times. I don't see how the War on Terrorism should set a new precident over those other times of war.