I have added the new original version (a small typo) and a version with what I think you want.
To be honest, I don't understand why. Why should everything be <desc xml:lang="en-US">? Isn't the purpose to support different languages and typesets? In this way I think you are restricting several typographic possibilities in foreign languages. Or I just misinterpret the xml:lang...
languages.xml
languages2.xml