Humor can't be defined as going downhill. Humor is really whatever you find "humorous" and if you don't think it's funny then you have a different sense of humor, and alot of people don't think it's funny, but alot do. Alot of people don't think Monty Python is funny but ALOT do. It doesn't mean American's have poor humor, it means you find the majority of their humor not appealing to you, but alot of people like it.