Access America has launched "Free-to-Go," a policy that covers travel impacted by a terrorist act. In particular, customers can be reimbursed for penalty or change fees if an incident occurs in the American city to which they're headed, within 30 days of departure. The policy also applies to travelers stranded for six hours or more -- regardless of destination -- as long as it's in the U.S. as a direct result of a terrorist incident within American borders. It also provides $1,000 to help them get back home as quickly as possible.
Traditionally, Travel Guard International insurance programs target bigger-ticket, international trips but now, in light of a renewed interest by Americans in staying within their borders (and within Canada's, as well), it's launched Travel America Plan. Pretty reasonably priced at $65 for two, customers get trip cancellation & interruption, travel delay, medical expense, missed connections, hotel overbooking and emergency medical evacuation.
As always when it comes to insurance, be sure to read the fine print to insure that policy fits your specific needs.