Kinetic energy is only taken into account when attacking air targets. Bombs that don't explode on the ground do no damage vs. structures at all (same as droptanks). However a bomb that hits a plane in midair will smash it.
To further elaborate on that matter, the actual kinetic energy of gun projectiles is only factored in vs air targets too. All damage vs ground structures is based on a fixed value, for example a .303 Browning round will always inflict the same damage on a structure (= an equivalent of 0.3125 lbs of bombs), regardless of range/velocity.