Surely I've heard it (in metro Atlanta), but I can't recall an instance. Even if not, I knew "instinctively" what "no worries" means...I probably wouldn't think twice if I heard someone say it.
There was some physics and/or philosophy book I read many years ago that started off with this quote (or if this isn't exact, something very close to it):
"What is matter?
Never mind...
What is mind?
No matter..."
So where did this thread start? (there's never an indication! I can SEE it's now in Office Party, but why does a mod moving a thread never say where it was moved FROM???)
FWIW, I think it should be moved (back?) to Grammar for Grasshoppers as a discussion of the international use of idioms. Anyone who disagrees can kiss my fa***.