NZ did a good job. Very different circumstances. Los Angeles alone has a population twice the size of NZ. New Jersey, where I live, has a population over 8 million with a population density of 1211 people per square mile. New Zealand is 47 per square mile.
It’s not easy managing a population of 330 million people in a country that stretches 3.8 million square miles. I don’t just mean in a pandemic. It’s whole separate cultures.
I don’t know if you live in NZ or were just using them as an example. The US Constitution is changeable but not in today’s political environment. You can’t get six people to agree on anything let alone 316 million.