David,
It appears to me that since you seem to meet all the aeronautical experience requirements for issuance of an FAA ATP except for the 250 hours of PIC experience, you are eligible for an ATP with the limitation prescribed by the relevant paragraph of 61.159 as displayed below.
Originally Posted by FAR 61.159
(d) An applicant is issued an airline transport pilot certificate with the limitation, “Holder does not meet the pilot in command aeronautical experience requirements of ICAO,” as prescribed under Article 39 of the Convention on International Civil Aviation, if the applicant does not meet the ICAO requirements contained in Annex 1 “Personnel Licensing” to the Convention on International Civil Aviation, but otherwise meets the aeronautical experience requirements of this section.
I am unable to view the text of ICAO annex 1 at the present time, but presume that your Mexican ATP meets all ICAO requirements other than the FAA 250 PIC requirement. I suggest that to verify your eligibility, you might consider doing either of the following:
Make an appointment to visit an FAA FSDO to review your qualification for an FAA ATP certificate.
Or;
Consult with an FAA designated examiner to review you qualification for an FAA ATP certificate.
Provided that the FAA agrees that you are eligible, then there are only two further steps to be accomplished:
Pass an FAA ATP knowledge test.
Pass the FAA ATP practical (flight) test.
Once the certificate with limitation is issued, the following applies to getting the limitation removed and a new certificate without the limitation issued:
Originally Posted by FAR 61.159
(e) An applicant is entitled to an airline transport pilot certificate without the ICAO limitation specified under paragraph (d) of this section when the applicant presents satisfactory evidence of having met the ICAO requirements under paragraph (d) of this section and otherwise meets the aeronautical experience requirements of this section.
Best of success to you and please post any new information regarding this issue here.
Best regards,
westhawk