The definition of an accident is well established on this side of the pond. The NTSB cannot call it an accident if it doesn't meet the definition.
Accident
As defined by the NTSB, this is an occurrence associated with the operation of an aircraft where as a result of the operation of an aircraft, any person (either inside or outside the aircraft) receives fatal or serious injury or any aircraft receives substantial damage. The occurrence is also not caused by the deliberate action of one or more persons and that leads to damage or injury. The NTSB definition, which is also used by the FAA, divides accidents into four categories:
Major - an accident in which a 14 CFR 121 aircraft was destroyed, there were multiple fatalities, or there was one fatality and a 14 CFR 121 aircraft was substantially damaged.
Serious - an accident in which there was either one fatality without substantial damage to a 14 CFR 121 aircraft, or there was at least one serious injury and a 14 CFR121 aircraft was substantially damaged.
Injury - a nonfatal accident with at least one serious injury and without substantial damage to a 14 CFR 121 aircraft.
Damage - an accident in which no person was killed or seriously injured, but in which any aircraft was substantially damaged.
Serious Injury
Injuries that result in one or more of the following conditions:
Requires hospitalization for more than 48 hours, commencing within seven days from the date the injury was received,
Results in a fracture of any bone (except simple fractures of fingers, toes, or nose),
Involves lacerations that cause severe hemorrhages, nerve, muscle, or tendon damage.
Involves injury to any internal organ, or
Involves second or third degree burns, or any burns affecting more than five percent of the body surface.
Substantial Damage
Damage or structural failure that negatively affects an aircraft's structural strength, performance, or flying characteristics, and which would require significant repair or replacement of the affected component or system. Substantial damage excludes damage to landing gear, wheels, tires, and flaps. It also excludes bent aerodynamic fairings, dents in the aircraft skin, small punctures in the aircraft skin, ground damage to propeller blades, or damage to only a single engine.