Manhunt 2 isn't in as dire a situation in the US as it is in the UK, but it's close. The ESRB has labeled Rockstar's controversial game with an AO "Adults Only" rating. If the game ships with this rating, most retailers will refuse to carry it, cutting sales massively. The only other console game to have an AO rating in stores? Grand Theft Auto: San Andreas, which was re-rated following the Hot Coffee scandal, and quickly re-released in an edited form.
Rockstar has the option to appeal the rating, or they can edit the game and resubmit it. We doubt they'll release the game at AO, because they like selling their products.