Your ability to get a job in the US as a "foreign educated" nurse depends a lot on where you are coming from. This may offend some readers, but employers do make judgments about the qualifications of prospective employees and try to hire only those who are going to "fit in" well and do a good job. Consciously or not, their judgment will be influenced by their opinion of the educational standards of your home country, any perceived cultural differences that might complicate your transition to an American workplace environment, and your English language skills.
Now ... coming from New Zealand, those possibilities for bias shouldn't be much of a problem in your case. You will have to work with one of the State Boards of Nursing though, to get a US license.
BSN's are usually not paid extra for their degree over the 2-year ADN nurses because the legal license is the same. However, we have LPN's (licensed practical nurses) who have a different license with less responsibility, who have attended school for approximately 18 months who make less money. However, a few hospitals do offer a little more money for the BSN, though it is very rarely a substantial amount.
Yes, a BSN is often required for any type of promotion or leadership position. However, a few years of practical experience at the entry level is also usually required.
I hope that helps a little. One of my best friends is graduate school is from New Zealand (now teaches in Aukland, I think) -- and she seemed to have no trouble going back and forth between the 2 countries. As graduate school opportunities used to be limited in New Zealand, I think you might find other faculty members who came to the US to study. They might be able to give you some good advice on the differences and making the transition successfully.