What's on tonight?

On cable-news prime-time lineups, national conversations, and why PBS won't ever be the BBC

The public often forgets that the United States is a giant country -- the world's third-largest by population, and literally continent-spanning in physical size. As a consequence, we often kid ourselves into believing that there is such a thing as a coherent "national conversation" happening from day to day.

■ But there are meaningful themes to what some like to call "the discourse", often centered around a handful of media institutions that have agenda-setting power, at least within ideological silos and socioeconomic clusters. Other countries have literal newspapers of record and generously funded national broadcasters; America has a predominantly commercial news industry that occasionally seems to spend as much time changing lineups as it does actually covering the news.

■ It is possible to believe, simultaneously, that the United States would probably be better off with a more prominent sector dedicated to public-interest journalism, and that it would be utterly impossible to competently administer anything like a national public-service media outlet. A self-governing people deserves to have a shared set of facts about current events and a modestly reasonable set of shared cultural values and norms.

■ Yet that's impossible here. Aside from the many and highly visible conflicts that emerge in the administration of public-service outlets in other countries (see, for instance, the perpetual heated debates over the future of the BBC or the scandal over secret payments made to a star of Ireland's RTE), the simple fact is that any outlet with enough sway to be considered a true national institutional voice would become the most contentious of "commanding heights".

■ PBS claims two million nightly viewers for the "NewsHour". Even the third-place commercial network nightly news captures more than twice that many. If PBS were drawing seven million viewers a night like ABC's "World News Tonight", someone would be making machinations to gain editorial control over it. And that's why it's basically impossible to imagine an American public broadcaster with the scale of the BBC.

■ It remains true that we are deserving of a high-quality national news agenda and news outlets dedicated first and foremost to public service. But we are too big and generally too contentious for that. And, ultimately, that probably saves us from what would probably be much uglier fights than we already get over who pays for "Sesame Street".