Although NZ has agreements with Aus and the US, you'll find on the ground that kiwis are actually not super fond of the US.
We won't let US nuclear ships into our waters, and we actually have quite a good relationship with China.
NZ is also quite self sufficient in many ways and so far from other countries that it's fairly sheltered from potential conflict.
I suspect the small size of the economy, the small number of people in it, and lack of strategic importance in military matters are what keep it protected from potential conflict more than it's self sufficiency and distance. In fact, if anything was to create conflict would be someone trying to capture that self-sufficiency to support their own population.
Small country, fairly neutral stance, little involvement in international conflict, and huge distance.
Follow that up with alliances and there's not much reason to come to NZ, other than for a holiday!