North American pumpkins are typically bred for decorative purposes (ie carving for jack-o-lanterns) but the pumpkins we would eat in NZ (and Oz) are more akin to a Hubbard squash. Pumpkins in either place are just a type of winter squash anyway – there are dozens of types w/only minimal differences in texture and flavour. So yeah, Australian pumpkins can be pretty readily swapped out with a Butternut or Buttercup squash, typical North American varieties. But they aren’t decorative gourds, lol.