America's workhorse bomber in the European Theater during World War II was the B-17, of which 12,726 were built.McManus should do some research and find out that America's workhorse bomber was actually the B-24 which was a more capable bomber. More B-24s, 18,000+, were built than any other plane.
Neilland's "The Bomber War" has an instructive anecdote about a Luftwaffe unit lining up to attack a B-17 formation and then seeing a B-24 formation off in the distance, which they promptly flew over to and attacked instead.