The red outline to the stars and bars was a short-lived addition between mid August and September 1st 1943. The RAF fin flash was a theatre marking for the MTO. The fin flash in the photo is of the wrong dimensions, being too tall and with the wrong proportions to the three colours (white should be narrow, one third the size of the red and blue).
I would guess it's been painted for a movie, and note the props, with the 'modern' metal finish, not black as per WW2 B25's.
Could possibly have been used, even if just for 'set dressing', in 'Catch 22'?
BTW, the helicopter is a S55 'Choctaw', known as 'Wessex' in the UK and Commonwealth.