Some parts of NZ are indeed captured (like the HRC) but mostly by ideological ideas rather than by wealthy sociopaths. Other parts are not. The two big parties mostly give you the same product in a different colored wrapper, and the mainstream media is a mouthpiece of the government and especially of the left (and we have really good underground media fighting back - Reality Check Radio).
But in my opinion, less of the infrastructure, the voting, the courts, etc, are captured. Small parties get into parliament and make a difference.
Also, according to the Economist Intelligence Unit, New Zealand ranks 2nd in terms of democracies at a score of 9.61, while the US is at 7.85 and falling. Greece, the Czech Republic, Estonia... all score higher than the USA.