There are over 50 different EMS certs in the U.S. with each state doing its own thing. The training for Paramedic ranges from 500 hours to two years depending on what state you want to reside in. You can contact the NREMT about taking the test with your education.
Here is an overview of all 50 states and their contact info.
http://www.emsresponder.com/survey/
What are the different levels of training in the US and also if anyones knows is someone from outside the US allowed to undertake the courses and the NREMT exams?
EMS qualifications are not recognized by the USCIS as a qualification worthy of a work permit.
Yes, because after all, being volunteer ambulance drivers for the fire dept isn't a worthwhile career.