As I think you know from the way you worked through it in your post:
Card issuer = irrelevant.
Currency paid = irrelevant.
Address of purchaser = essentially irrelevant.
Where the sale occurred, and who sold it to you - very important.
(Strictly speaking, the ticket place of issue could also be irrelevant, it would be the transaction details that mattered).
I've no idea if USA DOT regulations are limited to flights that have a USA city involved, but the place for a definitive answer would be a general USA orientated section of FT.
Not trying to be blunt, but a very small subset of the people who look in this section will be able to answer.