Get out your Bibles, and cross out "corn"

As I was researching Isaac Newton's determination of the original calendar date of the Crucifixion (the most scholarly thing I did all week, for sure) I noticed the mention of "corn."

A while back I heard a sermon in which the speaker referenced Biblical corn as well.

Corn?!

Corn is a New World crop, so why the heck are there 33 references to it, in both OT and NT?

Now, you probably know where this is going. It wasn't corn, the original Hebrew and Greek don't say "corn," they say grain.
But why not just say grain? Or phonetically translate the weird ancient word for it, like other hard to pronounce names and places?

According to a couple of commentaries I read, it's because the King James Translators knew that people of their time thought corn was really cool (because it was from the mysterious New World).
Then why do so many other modern translations still use "corn"? (Thankfully there are a number of English translations that say "grain") My theory is two fold: 1.American translators are USA-centric. Just like we counterintuitvely split Asia down the middle to make a world map with us in the center, so also do we think American corn is the best grain (it's in almost everything we eat). 2.Translators think we're smart enough to understand a triune God but too stupid to understand millet.