"Return to sender for correction. Country name must be in English on last line of address and not abbreviated."Hmm. So "Cuba" in Spanish, on the last line of the address, must be written in English, like this: "Cuba." Right. The way it was actually written. And apparently it can't be abbreviated as "Cuba." It's got to be "Republic of Cuba."
Like they can't tell "Cuba" from some other country? Sheesh. They certainly seem to be able to tell that "China" means "People's Republic of China" with no trouble, judging from the lack of returns from Asia. Maybe Cuba's a special case, providing particular literary challenges to the foreign-mail sorting machines and/or workers.
Thus confirming my suspicion that the people handling foreign-bound mail can't read, or at least, not very well.