Hi all, another cabotage question as this seems to be the thread of choice.

Does ticket stock or codeshare matter, or is it literally just if one of the legs is operated by a US carrier?

Example for clarity:
XXX - MEX on AM ticket, AM flight number, operated by Aerolitoral
MEX - JFK on AM ticket, AM flight number, operated by Delta

Also curious if somehow round trip or one-way made any difference?