"I think the Earth and the Moon have seen the same amount of pounding from space rocks. Intuitively, the magnitude of damage done to the lunar surface (single impact) would not be enough to shatter the Earth's mantle."

Hmm, I guess I was thinking more in terms of shockwaves- not big rock hit and make big crack in mantle:).
With large impactors- say 10 kilometer in diameter or larger most of it energy would tranformed into mechanical energy- causing large global earthquakes with largests earthquakes being felt at opposite side of the world. This is why you wouldn't want to shatter a large incoming rock- a larger percentage of it's energy would go into heating up Earth's atmosphere- turning the entire atmosphere into blast furnace temperatures.
The rocks I had in mind would larger than the one that killed the dinosaurs- rocks that hit Earth in the hundreds of millions of year category.
When a large rock hit the ground, it produces "tidal wave" in solid rock- the bigger and faster the rock the bigger "the wave".
As far as comparison to Moon or Mars. The Moon probably doesn't have a molten core, and if Mars does, it's quite small.
Now, a wave wouldn't necessary impart movement in Earth's plate. Analogy being a wave in an ocean generally doesn't move the water (other than up and down)- if a wave is cresting that's different matter.
So, not exactly sure how these shockwave could tranform their energy into lateral movement.