Sorry to add fuel to the tread drift of bombing accuracy - in the book "Inferno", the author (Joe Pappalardo) claims that a post war study comparing bombing accuracy between the RAF and the USAAF (IIRC, it was percentage of bombs within a given distance of the 'target'), the USAAF was better, but the difference was slight - as in about 1%.
According to what I've also read, the Norden had the capability of being very accurate, but that was with manufacturing tolerances what were impossible to meet in the sort of mass production that was required and with more knowledge of ambient conditions (especially wind speeds) than the bombers could possibly have in wartime.