Which united states have I visited? The most recent one was South Dakota; I drove on that morning into a random town I'd never heard of, and stumbled across the biggest gathering of bikers I've ever seen - Sturgis.
Not yet! American Samoa would be the easiest with direct flights from NZ to Samoa then connecting to one of the daily flights across to Pago Pago. Guam and Northern Marianas look remote; no idea how to get there! Puerto Rico and USVI I guess there's heaps of flights from the US mainland, so might do them next time I get to the eastern side of the States.
Well, if you decide to visit Puerto Rico or USVI, then good luck trying to not get infected. But, enjoy your stay, and hopefully find some English speaking citizens, as many will speak in Spanish :P