There's plenty of smart stuff on American TV too. The Sopranos, Dexter, Breaking Bad, Dead Like Me, Bones just to name a few. Then there's shit like Mighty Boosh in UK and Tim and Eric in US. There's stuff like Doctor Who in UK and Stargate in US.
You can't compare shows that are to be taken seriously, with shows that aren't. Mighty Boosh and Tim and Eric are basically the same kind of thing and you would compare them as a UK vs US kind of thing. You wouldn't compare House to Mighty Boosh.
Also I never said all American tv was garbage, I'm just saying Survivor, General Hospital, WWE, and Wipeout are considered to be very popular shows in the US. Appealing to the lowest common denominator, which seems to be less educated than the one in the UK and those we get less intelligent shows in general. There are exceptions.
Sidenote : Dead Like Me was freaking awesome I watched that and Eureka when I was in high school. You know, back when Sci Fi was spelled right and had good shows.
Actually Sci Fi is an excellent example, to get more viewership Sci Fi rebranded and started showing garbage to make more money. Granted Sci Fi still made terrible movies and showed them even then but you had great shows on that ultimately didn't appeal to the larger US market so you see them dumped in favor of Robot Combat League or Ghost Hunters or whatever the game show in the dark is. Now Sci Fi and other networks still manage to have a good show here or there but I think I've made my point.