There is actually no such thing like a conversion from ICAO ATP to FAA ATP, but the following link might help answering your question (it's an excerpt form the FARs = Federal Aviation Regulations) pay special attention to § 61.153 subparagraph (3).
eCFR ? Code of Federal Regulations
Regarding ATP Certification Program, check out the following link:
http://www.sportys.com/pilotshop/atp...m-atp-ctp.html