Haha! Yeah, I'm sure we Westerners butcher stuff from very foreign languages to us. But Spanish is just not that far removed, and it's so common in the new world. What bugs me most about mispronouncing "Antigua" is that it has to come from someone thinking they know better than most people (who would say it correctly by default, since the phonetics are obvious--well, maybe a short 'i' sound, but I can live with that). That's because when a 'G' comes before "UE" or "UI", the 'U' really is silent. That's the (absolutely inflexible) convention to get a hard 'G' sound before 'E' or 'I'. If you want to pronounce the 'U', you need 2 dots above the 'U' (in Spanish called "dieresis")--like this: Mayagüez (MAYA-GWEZ).
Remember the Mayagüez? It was a ship which was involved in some international big to-do quite a while back. Maybe you don't. It's been so long you were all probably too little, or not even born. But guess what? Most of the American reporters called it "MAYA-GHEZ", again thinking they were so fucking smart. That bugged the hell out of me too, because my mother's parents lived in Mayagüez, a town on the West part of Puerto Rico, for many years. I visited as a kid very often.
Edit: Jesus. The Mayagüez incident was in 1975. God, I'm old.