That's not consistent with the statement (not one you made; your post is internally consistent) that "America is a center-right nation" - a statement that gets broad agreement from all news outlets, I think. Certainly Fox reminds its viewers of that fact (or claim) whenever the R party has a bad day at the polls, and you can find the sentiment in CNN and MSNBC reportage (and many papers) as well.
If America is a "centre-right nation" - certainly it has a Gini number (measure of inequality) out of step with the rest of the developed West, a military budget that stands out as way different, and tax structures on high incomes that are different -- then reportage that most American news outlets would describe as "left leaning" would be "dead centre" in (almost all) other Western developed nations....which have a total population comfortably in excess of America's.
I mention other nations because the original post praised the BBC; this also clarifies the one respondent's complaint that the BBC is hardly "left leaning" but takes pains to be neutral. (I *can* get BBC here in Canada, where I would also say that the CBC, CTV, and Global networks here would all be described as "left leaning coverage" by most Americans...but we don't see it that way. I saw Paul Krugman worked over politely but very critically by a panel of three commentators on the BBC, who were all pretty skeptical of his negative views on Austerity; he gave as good as he got, but nobody would call it a lefty spin session.)
And I have to add that the almost universally recognized as "right-leaning" channel, Fox News, describes itself, not as right-leaning, but as Fair and Balanced - with pretty explicit statements by many of their staff that ALL other outlets are left-leaning so they have to step in an provide a truly factual, neutral viewpoint to serve the public better...but in a few cases (Jon Stewart I think?) their staff have been gotcha'd in conversation stating that they really are quite right-leaning...as a necessary counter-balance, of course, to all that leftism on every other channel.
Some other posters here seem to be attempting a discrimination between "leaning" as in editorial statements and as in their choice of WHAT topics to cover, purely factually. That is, you can be strictly factual about stories of "voter fraud" or "racist comments by old white men", while giving what many would call extreme amounts of airtime to a given topic, given its impact on the world.
I'm sure many would call me "left leaning" for stating my opinion that the "Democracy Now" program by Amy Goodman et all is pretty good at sticking to facts - it's their list of topic choices that differs from most other media. It's hard to call the Annenberg School for Communications a biased source, they're very highly respected (and the Annenberg's were the Reagan's best friends), and their dean remarked: "She's not an editorialist. She sticks to the facts... She provides points of view that make you think, and she comes at it by saying: 'Who are we not hearing from in the traditional media?"
I would say that BOTH editorial positions and choice of topics are both ways to lean; and indeed the news-topic way of leaning is more insidious than outright opinion, because people have their guard up more when opinion is clearly rather than implicitly the source of the content.