What country was bombed most in history?

Officially, North Vietnam (strategic bombing) & South Vietnam (tactical bombing). Un-officially, Laos & Cambodia. The air war was conducted by the USAF and USN over North Vietnam. North Vietnam countered with it's air defense systems: MIG 17, MIG 19, and MIG 21 intercepters; coupled with it's ground defenses: SAMs (Surface to Air Missiles) and AAA (Anti-Aircraft Artillery).