[Jamesy]

I think it's less to do with nationality and 'freedom of speech', and more to do with who the housemates actually are.

Look at the housemates themselves. Could you see any of the Brits being loud and obnoxious? No, because none of them (apart from James I guess) are like that. Look at the Americans, a few of them from reality TV shows that thrive on being over the top and outrageous. They are loud and obnoxious because it is Farrah, Jenna, Janice etc.. not because they're American.

Nationality accounts for the behavior on both sides in some ways, although I think it's more to do with the actual people we have in this series. You could easily have a load of quiet and content Americans, with a load of loud and obnoxious Brits.