I was mainly thinking about Project Thor, which roughly means that going at mach 10 (~3km/s) is like being made of TNT energy-wise. Now, current space-shuttles and the ISS weigh around 100 tons, and I'd imagine being able to get at least 10km/s, if not 30 with asteroid mining-level space tech, which should bring spaceships into the kiloton TNT range, that while far from a hydrogen bomb, packs the punch of a smallish fission nuke. So, while it probably won't be easy to wipe out big cities, immense damage is guaranteed.

What I can't estimate properly due to insufficient knowledge is the atmosphere's ability at stopping/limiting such threats, for all I know spaceships/rocks going at too steep an angle might blow up very high up, while stuff going at a gradual entry might be significantly slowed, Although as a rule, bigger things should care less about the atmosphere.

Edit: CellBioGuy's comment points out that spaceships aren't (and probably won't be) built to withstand reentry at dangerous velocities, making at least spaceship-jacks less of a threat.