@52N030W
So far I believe that I have to do:
- an FAA Medical
- ATP written
- ATP checkride (?)
FAA medical not needed for written but you will need for checkride and issue.
ATP written ,I found ASA books and software helpful(I had already finished UK CAA ATPL exams and study) scored 91% on FAA part 121 written after 6 month study( mainly on differences between regs)
Checkride,with your experience I would look at doing a reduced training type rating,less hours needed and alot cheaper than european,the oral test I have heard is the most challenging.
You will also need TSA security clearance sorted.
I'm still trying to get my hours required but several of my colleagues have gone down a similar route recently.