I recently had a short conversation with an American high school exchange student in Sydney who was annoyed about how much we are taught about Captain Cook and his voyages in Australian schools.
I tried to point out that Cook and the Endeavor were pretty damn significant to The United States also, but he was having none of it, and insisted that Cook was unimportant in US history. sigh.
Too bad it sounds like Endeavour will stay up there, but what an amazing find!
-Cultural relations between the UK and New Zealand have always been strong particularly back in 67 when decimalisation happened.
-Originally the 50c coin was going to be a design that paid tribute to NZ's farming industry but the designs were sent to an advisory committee for the UK Royal Mint who didn't like them. The new designs solicited in NZ resulted in the current 50c design.
-James Berry, the artist for the coins, was born in London before moving to NZ at around 20. Not that that makes him more anglocentric than a lot of the rest of the country (especially at the time).
-While Tasman was there first, his visit was brief and came to little result. Cook spent quite some time in NZ, mapped the entire coastline, returned later himself, and NZ was technically colonised shortly after.
-If you're concerned with the first humans to arrive there, they're celebrated on the 10c and 20c coin.
All in all, you might as well ask why Leif Erikson is so ignored in the US. The situations are fairly analogous.