Bombings and other terrist attacks happen on a weekly basis. Most of them get foiled in some way, shape or form by FBI, CIA, police, military, etc. If we had a war for every terrorist attack, we'd have died a long time ago.
But people are scared and some are going to demand some form of justice. They are going to become an interest group and Congress will have no choice but to resolve something.
People being scared isn't enough of a justification for a war on terror. Besides, Congress has shown before they don't listen to the public much, so it'll take more than one bombing to prompt major action.
