As long as the vehicle was legally sold, properly registered, licensed, and insured and every one in the vehicle is carrying the proper documentation I see no difference between you or I as a Canadian in crossing the US / Canadian border, in either direction. My wife is Australian, now a Canadian citizen, but never required a visa to enter the US but I'm not sure what the requirements may now be or whether it's different for Kiwis. Rather than rely on WAGs from those of us here on the forum you'd be far better sourcing accurate information from official Canadian & US government websites. Enjoy your visit! :B