This is a likely tempest in a teapot that Fox news will stir vigourously I’m sure. This will be bashed as a liberal biased movie.
Seems like maybe it is, John Cusack as Nixon doesn’t seem to work in my mind other than I suspect he really hates Nixon. I’m not sure he’d remember though.
Eisenhower is not cast yet, so I’ll suggest Gene Hackman, though he maybe too intense for likable Ike.
Harry Potter's Snape Could Play Ronnie to Jane Fonda's Nancy Reagan – Forbes.
Brucetheeconomist's Blog 
Hatred of Hanoi Jane has a long reach. Even in the military. I remember using a urinal once where a Hanoi Jane sticker helped soldiers “focus” their streams.
I can’t say I like her much either.