Trying to justify an AC group for terrorism is similiar to the Pentagon trying to justify F-22 to fight A.Q. non-existent airforce. The many AC groups of the U.S. is an anachronism of the cold war. Today the price is being paid because these irrelevant weapons platforms have diverted funds from extra soldiers and improved equipment for them.
You use what you have at your disposal to counter potential threats. Currently the US military is not geared for the asymmetrical warfare that it faces and as such continues to rely on tools better suited for power projection...having stated that, a carrier group still contains plenty of smaller platforms which are ideal for CT and Piracy related duties.