Do I need any types of visas to travel from USA to New Zealand via Australia? I am a US citizen.
Australia has a kind of quasi-visa very much like the US own ESTA, called Electronic Travel Authority. US citizens have to apply online in advance and pay a fee if they want to enter the country, even for a short visit.
But if you are only transiting through an Australian airport, don't need to leave the transit lounge and will leave within 8 hours of landing, you do not need a visa.
US citizens (and nationals) do not need a visa for a visit of up to 90 days in New Zealand.