IMHO there was no difference as although the US had the Norden bombsight which worked very well in testing in the USA, it did not work as well in the very different ETO.
Later as I understand it the US adopted bombing on a leaders signal. Given that the formations could be many miles long it is not conducive to precision bombing.
Perhaps the Dams raid was one of the first precision bombing raids of the war.
Pic is of a B17 we visited at Palm Springs Museum. My wife was appalled at how narrow it was inside and very emotional thinking of all those brave men risking their lives.
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