It was always an American company. In order to launch rockets from countries in the US sphere of influence (even from NZ), companies must obtain an FAA license.

Rocket technology itself is so intensely regulated by US export control laws that it’s practically impossible to develop an orbital launch vehicle without being a US- or Europe-registered company.

It is a real shame. It also looks like a lot of engineering work is shifting away from NZ — Auckland seems to be focusing more on operations and space systems, and the launch stuff is moving to the US with Neutron.