Why do Americans think shows like South Park, Family Guy are funny when they're nothing but vile adult shows?

"Comedy shows" like South Park, Family Guy, Futurama that Americans think are funny are nothing but vile crap. It is so ridiculous that it makes me want to cry more than laugh. It's only good for cheap laughs, not really funny and it truly represents how immature Americans are. Even shows like the "Colbert Report", "Jon Stewart Show" are not really that funny, but at least they're not vile crap and are funny. The only show that is funny in my opinion is the "Craig Ferguson Show".