I'm wondering if anybody could explain the function of the major 3 chord in the chorus of Imagine.
The progression goes like this:

F G C Cmaj7 E E7

Obviously the E and E7 chords are not part of the diatonic triads of the C major scale since they contain a G-sharp. Can somebody explain the use of this chord? More directly, where does it come from? It doesn't seem to be borrowed from a parallel mode or relative/parallel minor.

F G C Cmaj7 E E7

I'd analyze the E E7 pattern as a chromatic approach to F if this pattern is repeated. Sort of a secondary seventh VII/IV.