The US is not new to terrorism. September 11, 2001, Boston Marathon and others have terrorist connections and their impact was devastating. Not only did people lose lives but many businesses were effected catastrophically. Cantor Fitzgerald lost over 500 employees on September 11. It was a devastating blow but they not only survived, they have bounced back. They had a plan.
Businesses may not be able to stop terrorism but should be aware of it. While most businesses will not develop a plan specifically for terrorism, a DR plan that addresses major disasters can easily be tweaked to handle terror related situations.