I hadn't noticed that Americans are any more formal than Brits, and I doubt that it's true, on the whole. I'll have to start watching for examples.

If you're quoting TV announcers or news reporters, I'd guess that they're using titles by way of explaining who the people are. Standard journalistic practice is to use the full name and title of a person the first time he is mentioned in an article, and afterwards refer to him only by his last name.

Here's how 4 newspapers treat the same story. I see that styles vary somewhat, but I would hesitate to characterize either the UK or the US as more formal:

From the Guardian (UK):

Barack Obama today becomes the first sitting US president to make a studio appearance on a daytime television chatshow....

Obama's third appearance on ABC's The View....

From The Telegraph (UK):

President Barack Obama replied "where do I begin here?" when asked how difficult....

... the president was asked....

The president also praised....

From the New York Times:

President Obama will be joining the hosts of "The View" this week....

Mr. Obama's chat with the unpredictable co-hosts....

[The Times' style is unique in the US, as far as I know, in that they always use "Mr/Ms" etc. on subsequent mentions.]

From the St. Paul Pioneer Press/Associated Press:

ABC's "The View" has welcomed many notable guests, but none more prominent than President Barack Obama....

They said the majority of the hour will be devoted to Obama's appearance....