Guess we don't need them anymore, I feel we should.
In Japan, text messages are sent to your phone and TV's can turn on by themselves displaying the latest news to warn you of dangers.
Problem with air raid sirens - only really works when a population is properly drilled to respond to them which only really happens when you are well into an actual war/disaster or faced with an ongoing significant threat of disaster.
Generally we are pretty poorly prepared for any kind of significant disaster in this country.