Opera singers should learn to speak the language if they are going to sing in the US.
Why should opera singers perform
Le nozze di Figaro,
Don Giovanni, or
Die Zauberflöte in English? They were written in Italian or German, and the lyrics and music work best together that way, IMHO. I don't think this makes any more sense than dubbing, let's say, Italian or Chinese translations onto a Merle Haggard song. Great music - including opera or Haggard - transcends written language if you just listen to it empathetically. IMHO, of course.
I really think the subject of singers is far afield from "What's wrong with country music?". Just like in
any style, there are now good and bad singers - there always have been, and there probably always will be. For the most part, the vast majority of country singers are not "great singers" - not at all. Some of them - even some of the well known ones - have (or had) a lot of trouble carrying a melody. That doesn't bother me - they're purely stylists and it works in the style. But the great opera singers you blithely write off as "screeching" are truly great singers. You don't have to like it, but to write them off as screechers is profoundly inaccurate.
In my opinion, great instrumentalists are the ones who succeed in making their instrument "sing" in a way that recalls the human voice, in its many manifestations. I would infinitely rather hear tasteful steel guitar backup of a good singer - country or otherwise - to the 1,439,732[sup]nd[/sup] rendition of Steel Guitar Rag.