That would be an interesting analysis to see, my guess is it wouldn't be that different than if it was a sphere of equivalent mass, and vs a 400m sphere would be 400/(4*pi*200^3/3) = .0012% the volume (and so kinetic energy), and it would not penetrate in a way that does specifically worse damage. Just guessing though.
Edit: I confused radius and diameter in my calculation and revised it. I may have made other mistakes
That would highly depend on what the composition of the asteroid was and where it impacted. On a fault line? In the middle of an ocean, or a city?
For sure the depth of penetration would be different for a rod shaped object of equivalent mass compared to a spheroid, the latter would penetrate much less deep. Angle of incidence would be a factor as well as (obviously) the speed of the impacting body. But if it impacted at a higher speed than that the ejecta could get out of the way it would cause an absolutely massive crater. As though you'd exploded an absolutely enormous nuclear bomb deep underground, but not so deep that the explosion would still reach the surface. That would probably be the worst case scenario for an impact like this.
Without fins, it's unlikely to go straight in. It would start tumbling, and probably break up and burn up. A sphere would more likely get to the surface intact.
If it has the same density than earth, it wont pierce deeper than its length. If it is made of uranium a bit over twice that (assuming earth is made of iron).
I wonder if there have been any simulations of such an impact and what the worst case would look like for equivalent mass but different shapes and asteroid compositions.
