United states or New Zealand for Medical School

Hi, i am an undergraduate at an American University. My goal is to go to medical school in the United states or New Zealand and then eventually end up practicing in New Zealand. I am a Citizen of the U.S and therefore med school will be much cheaper if i go here in the U.S as well as easier to get into. However i don't know how easy it is to get into a Residency program in New Zealand with an M.D. Would it be better for me to just go to Med school in New Zealand. Any advice helps.
Thanks