LPN Looking to work in the USA. Where to Start?

Hi, just some questions I'd like to ask about working as an LPN in the USA. I'm an LPN graduate from Alberta Canada but am presently employed in Saskatchewan. I had no problems changing licensing bodies from these two provinces but now I am looking to work as an LPN in the USA and don't know where to start? From what I've read I have to go through some sort of Visa Screen and write another exam to work in the US? Does anyone know where I start with this? Are there websites I can go to to start this process? How do I right this exam and once I have written it, is it good for all states in the US like our LPN National Exam? Can I start the Visa screen without having a job in the US already? So many questions and I have no idea where to start? Any help would be greatly appreciated. Thank you