I've read a lot about Jack Northrop's work on his flying
wings and I think the USAF could have had an effective
aluminum skined version by the late 1950’s if it wasn't so
politically unacceptable to the top brass in the USAF at
the time.
There were two major complaints about the Northrop YB-49’s
that the brass used as an excuse to stop development of the
planes.
1) The bombadiers found it almost impossilbe to hold a
steady course on target because of the hyper sensitivity of
the rudders under manual control which caused excessive
yawing back and forth left to right.
2) The bombays had been designed for conventional bombs of
the day and were not big enough for the new nuclear bombs.
Both of these problems could have been overcome by
inclusion of a autopilot to dampen the excess yaw and
enlarging the bombays.
But the real problem was that most of the top brass just
didn't like the way the flying wing looked. It didn't look
like what they thought a bomber should look like.
Instead they went with the Convair B-36 which in my opinion
was not a very successful design.