What can NZ do to US? Find alternative supply routes for the current trade with US, embargo it and expell its diplomats until US cease any support for Israel, break diplomatic ties and sanction it. Now NZ alone can't do much, but it can show others it is possible to do even small part of what Yemen are doing (and don't forget that Yemen WON against, according to US military itself "the biggest naval operation since WW2"), so the other sincere states can take the example. And when enough of them will do it, the US as imperialist nation will feel that deeply.

And it isn't even this farfetched, just 10 years ago US hegemony was seemingly solid and now countries like fucking KSA are doing unthinkable things which just 13 and 21 years ago led to destruction of nations trying the same.

Of course we both know that NZ won't do this, just as my Poland also won't, but the reason for that is probably not the subject of this question.