You're absolutely correct. I should have phrased it better.
I should have said: The World's finest, and the World's FIRST independent Air Force. That would have been more accurate.
Thanks.
Edited to add:
The Royal Air Force was formed on 1st Apr 1918. The US Air Force was formed on 18th Sep 1947.
Incidentally, this is why it is never necessary to refer to it as the 'British' Royal Air Force, as one might refer to the Royal Canadian/Australian/New Zealand etc Air Forces.
It is simply THE Royal Air Force! Because that's what it is.
It's what it says on the tin.