The BBFC still exists today and serves pretty much the same purpose as the MPA in the land of the free. Is there any practical difference between the two?
over in the US, getting an MPAA rating is completely voluntary. MPAA rules do not allow it to refuse to rate a motion picture, and even if they did, the consequences would be the same as choosing not to get a rating.
If you don't get a rating in the US, some theatres and retailers may decline to show/sell your film, but you can always do direct sales, and/or set up private showings.