re: What plan does NASA have for an asteroid headed straight for us?

It's an interesting questions. I would assume at this point there is no plan on paper for such an incident without knowing the size and mass of the asteroid.

I like to believe that we have a good month or two of warning before it hit that we could identify where it will strike and get the area evacuated. In the case of one large enough to alter the scope of humanity, well... God's will is God's will.