It is normally short haul flights that get affected more than long hauls as a lot of the time the crew are coming in from somewhere else and if they get held up it knocks onto the next flight.
With long the crew are normally starting their duty at that airport and not from somewhere else. Likewise the aircraft would have come from the other side of the world and not be so affected by restricions etc.
It is also easier to cancel a short haul rotation as it will on many occasions be the same crew taking the aircraft out and then back in again later in the day so it knocks straight out inseatd of rolling onto another crew etc.