If you watched enough Simpsons episodes, you pretty much should know how TV execs think. Heck, the Poochie episode is the best distilled commentary on TV executive dimwit thinking I've ever seen.
My overall point is, American TV execs on stations like say Fox or NBC have far more creative control over their shows than a TV executive working in the most popular TV station in say, France or England. So if we say some show like Lost or Heroes is going downhill, at least half the blame should conceivably be put on the shoulders of the network they are airing in.
Thankfully, TV execs are less meddling on cable-only stations.
But this is why international shows never fail to be censored or even structurally altered in some way once it reaches U.S. shores but somehow miraculously runs virtually untouched in every other country outside of North America.