Asteroids, meteors pass by, burn up in our atmosphere all the time. Occasionally one hits the planet. I like the movie Armageddon paraphrase: we have barely enough to scan 3% of the sky and its a big sky. If we are lucky enough to see a ELE (extinction level event) coming at us, we probably won't have more than a few days to make peace with our ecology. At least we are here now.
I doubt we will ever be ready for a major asteroid strike, unless kissing my ass goodbye is considered ready.