Back some 60 million years and before, the solar system was still developing and there were just billions of rocks and dirty ice balls just in some orbit around the sun, not counting the billions that came from outside.
All this time passes and many were cleaned away by the planets, Moons,Earth, and the sun, so that now, only a few hundred resident asteroids and comets remain.
Now nobody knows for certain where this 7 mile wide rock came from, we only know the direction of impact and the massive energy it packed. Seems there have been other similar impacts on earth in far history.
Back then, raining rocks was probably common. Even today, the earth gets pelted by small rocks that don't incinerate in the atmosphere, maybe on a daily basis. Too small to do much damage, a couple people have been hit resulting in injury, coming through the roof of houses, denting cars fairly good.
Yep, you look at the moon, a great many of the craters were from meteorite or small comet strikes, millions.
With no atmosphere, earth would hardly look different. There are 128 significant craters on Earth today, they are quite a sight and you might visit one. I have seen the Arizona crater near Winslow, and WOW, that was some rock.
Consider, the dino killer hit long before humans ever walked earth.