"The Night the City Screamed," ABC's Sunday Night Movie at 9 on Channel 7, is really a two-hour round of Celebrity Looting. Larry Brody's episodic script details the effects of a big-city blackout on selected local gentry; although many use it as license to pillage, the various stories lead to an affirmative fade-out glowing with interracial harmony.

In the star-heavy cast, no star looks heavier than the magnificent Raymond Burr, who, if he gets any bigger, may qualify to be the object of the next Voyager orbit. Burr has only a few scenes as the mayor, but he looks and acts more like a mayor than most mayors do. As his second-in-command, Georg Stanford Brown contributes another thoughtful, accomplished performance, even in these potboiler -- or maybe parboiler -- surroundings.

David Cassidy and Clifton Davis play cops trying to cope; Robert Culp is effectively oily as a grandstanding councilman; and Linda Purl plays, very smartly, the daughter of an inner-city storekeeper.

Among the recurring scenes, the most accidentally funny is set aboard a trapped elevator in which a man keeps shouting "Please! I have to get out of here!" After this happens three or four times, a woman doctor on board finally has the presence of mind to administer the old "I-needed-that" slap in the kisser. When it's suggested on the elevator that the passengers sing to avert panic, one fellow says, "How about that new Bee Gees song?" And there you have it -- sheer, stark-raving TERROR. 'Manor Born'

In "To the Manor Born," an imported British comedy serial premiering Sunday at 10 on Channel 26, financial peril is signaled by a drastic measure -- the hostess at Grantley Manor begins economizing on the sherry. In the first episode of Peter Spence's story, her husband has dropped quite, quite dead and his widow, who loved the old estate more than she loved him, sets about trying to protect it from its brash new owner.

Penelope Keith, than whom few Britishers are Britisher, plays the widow with as much spunky pluck as Mary Poppins and Miss Marple put together. The humor is hardly on the hilarious level of a "Fawlty Towers," but compared to the high decibel range of most American sitcoms, the show's quietly amusing demeanor may strike many people as more than welcome, indeed.