American films curse a lot more than real Americans do. In real life most Americans I know almost never curse. They certainly curse a heck of a lot less than back home. They also consider words "swear words" that I would consider safe in UK.
Using words like "hell, damn, and stupid" would get you detention in school. When my kids refer to the "s word" they're still referring to "stupid".
There are some people that curse but it's much more heavily frowned upon here... of course that might be in part because this is the South.
I did a quick poll of 3 coworkers (all I dared ask) if they knew or ever used the word twat.
One said "of course I know that word that's what Monty python says".
One said he knew the word but wouldn't use it unless he was imitating a British person.
The third said he'd never heard of the word and was bemused why use that instead of ****.