It's not something I have had to worry about, given I fly out of Seattle. As such, I attach pre-check to my flight out of Seattle and then don't have to go through security in LAX, SFO (depending on airline) or YVR. Coming back, I always have pre-check lined up for the flight back to SEA, so again it's not an issue at LAX or SFO. Thus, of North Americans (at least based on my experiences), mainly only those who originate in one of the cities NZ flies to have to worry about it.