There is no way to get a FAA ATP based on your JAR ATPL. The FAA will issue you a private VFR only certificate based on your JAR license. You can take a simple knowledge test and have an IR added without a checkride. The only way to get the FAA ATP is to pass the ATP knowledge test and pass an ATP checkride.
Why call the FSDO, you call read the same book the FAA Inspectors use here:
FSIMS Document Viewer