Need career advice, direction!

I am a BSN nurse and have been working for 4 years only. During that time I have worked ICU and ER both at level on trauma centers. Currently I work for a French NGO doing relief work mostly in Africa. Of course, I can not do this forever, and I have started to think that going back to the Emergency room is not totally appealing either. Much of my work in Africa has been not actual nursing, but training local staff how to nurse, monitor and otherwise take care of patients (ie think: don't yell at the mother, try to explain to her nicely why she should not remove that NG tube!). I have really loved to see people develop new skills and also learn to really support patients.
So, Now, I am looking for what I can do beyond this. I started an MPH, and found it was mostly statistics which of course I did not like. So, now I am thinking about getting a PhD in Nursing which would allow me to be an instructor in the US. I have heard there are instructor shortages.
Is this an option that makes sense? And is there any way I could do some of the course work on line or independently while I am in Africa?