Wire amapacity, material reaction to environments, grounding and bonding theory, step potentials, surge protection... the list goes on. If for example one sits down to study TT, TN-C-S, TN-S and IT earthing it opens the door to a whole new level of understanding the reasoning behind our article 250. An easy example is TT earthing, which rids the old belief that a ground rod can clear a normal breaker.
Canadian and American wiring is very similar so I'm far more inclined to be interested in what they do than the British. That being said, there is only so much that can be learned about other systems before it becomes and unprofitable waste of time.
Similar, but very different in application. Nothing in the NEC would allow fixed non motor loads having no integral overload protection to load #12 to 25 amps with a 35 amp OCPD.
In any case the laws of physics remain the same.