If I am not mistaken, I am very sure Delta(or one of it's Regionals) flies a few flights to Mexico from DFW.
In the early-mid 90's, Delta operated a few Trans-Atlantics from DFW. Unfortunately, they decided to lower the status of DFW and pretty much drop all long-hauls including their HNL flight which ended a little less than a year ago with the L1011 retirement.
American pretty much beats them in all categories.
As for flights, I think Delta has around 100-150 vs. AA's 700 or so flights.
Delta really withdrew DFW because AA outisized them as a hub carrier. AA has a wide range of long hauls that have done pretty well for them, unlike Delta, because American has more domestic feed.
Give me a break, I created this username when I was a kid...