The risk of asteroid impact is near zero. But it exists.

"Asteroid 2024 YR4 no longer poses a real threat to Earth, though it still has a slim chance of hitting the Moon in 2032. NASA is using the event to refine its planetary defense strategies and gather more data with advanced telescopes. Credit: SciTechDaily.com" (ScitechDaily, Asteroid Alert: NASA Drops Impact Risk to Near Zero, But There’s One Small Catch)

The risk of asteroid impact is near zero. But there is a small possibility that something hits asteroid, and changes its course. The most feared things. That we might not have time to react to are small. And, maybe ship or smaller asteroids that courses can transfer easier. The impact from satellites can also turn those small asteroids into another trajectory. 

The Liberty Statue's size asteroids are things that can destroy entire cities. And it's a small possibility. That some satellites or some other small asteroids hit it at a critical point and push that asteroid to Earth. 

Another thing is that an asteroid that changes its trajectory from Venus or the Sun and comes from the Sun's direction can stay unseen. Those, maybe very small objects can cause risk in a very short reaction time. Can those objects cause danger on Earth? The material that forms an asteroid, its shape, and its speed are things that determine: does it comes even near the Earth's surface. 

The small asteroids can detect only a couple of hours before they impact. But changing their course is not very difficult. The small space shuttle can pull a mylar bag over them and then pull them away from their trajectory. Large ice asteroids can be vaporized using small nuclear weapons. The spacecraft's rocket engines can also turn that ice to vapor. The spacecraft can also dock the rocket to the asteroid and push it gently to another trajectory. 

There is the possibility of turning the trajectory of the large asteroids by detonating a series of neutron bombs on another side of the asteroid. Those impulses can turn the asteroid's trajectory. Or if there is some kind of ocean in the asteroid's shell. The nuclear detonator can make a hole in the ice. And then that water can turn the asteroid's trajectory. 

 https://scitechdaily.com/asteroid-alert-nasa-drops-impact-risk-to-near-zero-but-theres-one-small-catch/