It’s not necessarily the size of an asteroid that determines whether it will survive entering the atmosphere, but the composition of it. In other words there are small ones that survive and comparatively larger ones that don’t. But, a mile wide one for instance is going to be a big problem no matter what it’s composition might be.
Stuff hit’s the Earth’s atmosphere all day. Most of it burns up and we down here don’t even notice it. Now and then something big flies by and keeps on going. We’re lucky in that the planet Jupiter acts as a kind of a cosmic shortstop pulling in stuff that would other wise come slamming into us. Like Comet Shoemaker-Levy 9 in 1994. Had that bad boy hit us it would have been game over, done, finished. We do get lucky most of the time but fact is we’re going to get nailed someday, big time. Not a question of ‘’if’’ but ‘’when’’. It will happen .
North Korea didnt have a successful missile launch until we landed that thing. I want to believe that we shot them down seconds after launch.