Even an asteroid only a few hundred feet wide would have an impact powerful enough to wipe out a city. And the bad news doesn’t end there either.
The Odds (and Potential Damage) of an Asteroid Hitting Earth
Of course the damage a given asteroid would inflict on Earth would depend wholly on its size. A six-mile-wide asteroid like the one that wiped out the dinosaurs, for example, would have the same impact it did 66 million years ago; meaning it’d wipe out essentially all life on Earth’s surface.