Difunto usually describes a person who has died, so it is an unexpectedly dramatic word to find in a love song. Here, in "este amor difunto" ("this dead love"), it is used metaphorically to say that the relationship has ended and is no longer alive.
MC Davo and C.R.O. spend this song asking one question: "¿Por qué será? Que esto me duele tanto" (Why is it that this hurts so much?). The chorus is a patient, slightly dramatic kind of heartbreak. "Si es por ti, un par de siglos aguanto" (If it's for you, I'll hold out a couple of centuries), and the sting at the end of it, "Siempre te estoy soñando y no estás cuando me levanto" (I'm always dreaming of you and you're not there when I wake up).
The verses are less patient. He is up late, smoking alone in his room, and his fans ask "¿por qué ando triste en el meet & greet?" (why am I sad at the meet and greet?), which is a funny, very modern detail. Listen for the slang: "no aguanto vara" is Mexican for "I can't take it anymore", na' más is nada más (just, only), and terminamo' drops the final s of terminamos. The closing shout-out, "Argentina y México", names the two artists' home countries.