I find your argument largely derivative of similar arguments William has made in the past, particularly in regards to That 70's Show. So an American blogger rips off the argument of a British blogger about American TV ripping off British TV? That's some zen shit there, my friends. I think I just heard a tree falling in a forest.
I'm assuming you don't watch enough BBC to notice the incredible short life spans of most British TV shows. Here in lies the answer to your question.
According to the internet, the BBC operates through public funding. Strictly speaking, they are not a business. When some witty Brit has a humdinger (I wish I knew some British slang) of an idea they pitch the idea and with little consideration of commercial success the best ideas are plucked out from an immense pool of talent. If picked up the show creators get busy making some TV. Ratings are certainly a concern but not from a revenue sense leaving creators with greater control. Shows rarely have a team of writers so after a one or two season burst of creativity most shows die because their creators are tired of doing them or have simply run out of ideas. The network has no economic incentive to milk the show so something new takes it's place.
This is over-simplified but demonstrates why British TV is inevitable more innovative then American. It should also be noted it's almost impossible to break into British TV if you aren't British since the BBC's mission serves the people. This partially explains America's aversion to such a system. That and a dogmatic dismissal of certain strands of socialism.
Meanwhile, American TV networks invest significantly more time and money into their shows. If someone walked into your office asking for $10 million to make a car show you'd wonder who the hell will watch it. Another guys comes in with a hit British TV show and gaudy ratings numbers to widely gesticulate at and he asks for $10 million? Well, which decision would you rather have to defend when the show fails and your job's on the line?
R.E.M., Modest Mouse and The National are touring together this summer. This is the most important thing to ever happen.