Americans and their "ah-due"

What is it with Americans and their butchery of basic English semantics and pronunciation?

It's "I couldn't care less", not "I could care less." Think about it logically for a second or two and you'll find that the latter makes no sense at all.

Also, don't say "Without further a-due". It's "ado", people. Ah-doo, not a-due! Ever heard of that Shakespeare play?

And while we're on the subject:

Coup de grâce is pronounced "Coo-duh-grass", not "Coo-duh-grah." French may sometimes be confusing in terms of pronunciation, but -ce endings are never silent. Vide e.g. fem. name Alice.