Cable news in the United States is loud in every way. Congressional hearings are packaged up like soap operas and presidential debates promoted in a style typically reserved for action movie releases. To the uninitiated, the exertion could reasonably seem unsustainable. Americans, though, know better.  And so it was, last Thursday, that on the third consecutive night of nonstop US presidential election coverage, footage of MSNBC’s Steve Kornacki leafing through sheets and dragging maps across screens (the “Kornacki Cam” even visible inset during ad breaks and reminiscent of the kind of passive, novelty broadcasting carried out by zoos) was still…