Why are American talk shows so much worse than British ones?

Sam Enright emails me:

My girlfriend is American, and she’s been struck by how the UK panel shows – QI, Would I Lie to You, 8 Out of 10 Cats – are so much better than the American ones, and play to the lowest common denominator less. There don’t seem to be a lot of panel shows in America per se, but the closest thing is late night shows, and so far as I can tell, they’re all terrible. A lot of whining about politics. Previously good comedians like Trevor Noah or John Oliver seem to become remarkably un-funny upon becoming hosts of US shows. Yet America has no deficit in producing quality films and TV in general. Do you have a theory about this? Are there culture-specific cues that I’m not picking up on? Is the American elite more competitive and therefore more politically unified, and does this filter down to there being a remarkably narrow range of views you can implicitly endorse in American comedy? Is it all just that the BBC has good taste in what it funds?

I don’t watch enough television to have an informed opinion, but my general intuition is often that the American market has all sorts of hidden corners and niches, many of them stupid, so often there are especially high returns to “selling out.”  In Britain, maybe it is more the case that “the TV customers you see are the TV customers you get”?  This hypothesis, while it can lead to cultural dumbing down, is also consistent with the U.S. market as especially good for new product introduction, and not just because population is high.  Any opinions on the TV issue?