Perhaps you are not aware of the fact that due to air travel New Zealand has a thriving tourism industry that bring millions of visitors every year. The reason they only had 25 deaths is because of the actions their excellent government took.
The Flu pandemic you referred to was actually the 1969/70 so called Hong Kong flu epidemic which was a mutation of an existing Flu virus. The Covid 19 infection rate is twice as virulent as the Hong Kong Flu.
Sweden has the 12th highest death rate per capita in the world and their infection rate is currently increasing. Comparing the Nordic countries is interesting as Sweden allowed its infection rate to increase whilst Norway Denmark and Finland all took a more interventionist approach. This is reflected in the death rates from Covid in these Countries :- Sweden-5899, Denmark-674, Finland-346, Norway-277.
What I find most difficult to understand about the “herd immunity” approach as advocated by Trump among others is the callous disregard for the most vulnerable in society. As with most on this forum, I have had my fair share of economic hardship and the loss of close relatives and friends. I have no doubt which was most difficult to cope with.