CBS SHOULD HAVE TAKEN note after the failure last fall of sci-fi drama Threshold—not to mention ABC's Invasion and Night Stalker and NBC's Surface. But this year, the net introduces Jericho, the confusing tale of a nuclear mushroom cloud creating havoc in a small Kansas town. Jericho faces off opposite the hasty, last-minute arrival of new NBC sitcoms 20 Good Years and 30 Rock (which were originally scheduled one hour later), and three established hours—ABC's Dancing With the Stars, Fox's Bones and America's Next Top Model on CW. With the three established hours all young and healthy, the question to ponder is this: Will there be an audience left for Jericho or the two comedies? In defense of NBC (which sure could use a break these days), 20 Good Years and 30 Rock (which was given an early "thumbs up" by many buyers) are the only comedies in the hour, and that could make a difference—a very big difference. Since a five-minute clip of Jericho at CBS' upfront had buyers scratching their heads, one has to wonder if the public response will be any different. At 8 p.m. in midweek, chances are it won't be. Although no one expects two unproven NBC comedies to move to the top of the charts, counter-programming is everything, and NBC was wise to open the night with comedies. Move over, Jericho.