We have 9 years to figure out what to do. Hitting the earth may not be as bad as if it hits the moon. That would cause more trouble. If it hits our atmosphere its likely to recoche away. Its also likely to split up, burn up and hit the ocean. These would all have some affects on us. But are not likely to be dinosaur extinction event. I could happen. Just not likely. But if it hits the moon, we have a bigger problem. The moon does not have a protective atmosphere. And it would likely change the orbit of the moon or maybe cause the moon to splinter. This could be a real issue with much wider ramifications.
“Space 1999”—Earth’s moon is knocked out of orbit by a gigantic explosion.
Actual worst case is an asteroid impact along the continental shelf, off the coast. Tsunami, incandescent debris, secondary fires, salty rain for a few possibilities. Then there’s Mothra.