I'm not sure he came across any worse than O'Reilly did; shouting people down and not letting them finish is just bullying, not discussion. Though I suspect that's par for the course for O'Reilly, from what I've seen. It wasn't so much an interview as an excuse to rail on the guy for five minutes.
Bill O'Reilly is terrible and your analysis is pretty much spot on. In general, anything from Fox "News" should be taken with a grain of salt.
In the UK many churchgoers only attend once or twice a year, and attendance has been steadily dropping for decades. How much of the US is privately secular, but conforms to social pressure to attend church? Is there anyone from the US who is willing to share their experience?
There are a few dynamics at play in the US. First, yes, your observation is consistent with my experience here. A lot of people identify with the religion of their youth or the religion of their parents, but do not strictly adhere to doctrines. A lot of my friends call themselves religious, but they engage in premarital sex. Or are openly gay. Or any number of other things their faiths forbid. So while it provides an identity and a social group, it does not factor heavily into their daily priorities. However, despite these inconsistencies, people still cling to that identity (ie, calling yourself an atheist is political suicide).
Second, in a lot of the US there is a trend towards diversity. For example, within about an hour of where I live I can find respective places of worship for Christians of all denominations (including Mormons, Jehovah's Witnesses, etc), Jews, Muslims, Buddhists of multiple traditions, Sikhs, Amish, Hindus, Scientologists, and probably a lot more that I haven't personally seen. This trend does not hold in some areas, such as the southeastern US (the "Bible Belt"), but does for most of the country. Many of these religious centers have just been established within the past 30 years or so, so they enjoy increased attendance from their founding generation. However, almost all faiths I have interacted with show a decline in attendance by youth who were born here.
Last, as a reaction to the first two (among other things), in the late 70s there was a resurgence of religious fundamentalism. This exploded in the mid-to-late 80s. These are the geniuses who believe the world is only 5,000 years old, bomb abortion clinics, and protest the funerals of soldiers who have been killed in action. Ironically, the emergence of this group has pushed many former moderates into the secular realm, feeding the first observation above.
So, to summarize, while our church attendance may appear to be higher in the US, we are also trending towards secularism.