Worth pointing out also that NMC registration requires at least one year work experience as an RN. So, you would still have to work for at least a year in the US even before starting the NMC...
I've had a positive PPD since I was 13. I have no idea how I was exposed. I've always had normal chest x-rays. However, the one I had two years ago was misread which resulted in my having a CT scan...