I'm intrigued that the RAF assets the US allegedly considered 'essential' amounted to:
3 x Canberra (now retired)
3 x R1
About a dozen ancient tankers
Er, that's it. So can we assume the US considered the other 95% of the RAF a complete waste of space?
I'm well aware USN/USMC use the same refueling system as the RAF. I'm also well aware that some 100 USAF tankers are permanently fitted with that system, and that any of several hundred KC135s can easily be converted to a P&D system by the simple expedient of removing the lower half of the boom and replacing it with a hose. Not ideal, but it works. The idea that the RAF's tanker fleet was 'essential' to the Afghan ops is absurd - USAF could easily have done it if it needed to.
As SASless pointed out, a single squadron of B1/B2/B52 has more striking power than the entire RAF.