The goof occurs when Yo-yo, Milo, and Orr visit the Caliph of Oran in Algeria; there never was such a thing as Algeria was a French colony until 1962. Furthermore, Algerians never dressed as they are depicted in the series.
Yossarian fails to drop his bombs during his B-25s first pass over a bridge. The pilot is not aware of this until Yossarian reveals it. This is extremely unlikely- The usual bomb load would have been over 3000 pounds, which was more than 10% of the max takeoff weight. Typically, the bomber would experience a rapid gain in altitude upon dropping its bombs.