Every American family should see "Holocaust." It is the most powerful film ever made for television. But the immediate practical concern for the NBC Television Newwork is not how many American families but how many Nielsen families see "Holocaust" when the 9 1/2-hour drama about the Nazi extermination of European Jews is televised over a four-night period beginning Sunday.

This is pivotal moment for television.The ratings of "Holocaust" could affect programming decisions for years to come. Networks will study them as indicators of whether TV viewers can be lured from the usual numb escapism for something grim, provocative and emotionally demanding. Normally TV offers fast , fast, fast relief from pain; "Holocaust" opens an old would that much of the world has spent three decades trying to forget.

We are at the crossroads. Network competition has grown too relentless to allow for philanthropic gestures that don't draw viewers in the required tens of millions. "Holocaust" will help determine whether TV is to be exclusively the national font of fun or a medium in which the difficult and the troubling also can be expressed to a "Holocaust" is not unrelieved woe, but it is a times a shattering congfrontation with the darkest components of the human condition, and it ironically comes at the end of a TV season in which the silly, the vapid and the puerile have thrived without challenge.

"If it fails on the same magnitude as 'King,' if it is what's considered a colossal failure," says "Holocaust" producer Robert Berger, "that means it could still have been seen, at least in part, by 65 million people. Failure in television is a relative thing. If it is a success, though, that would encourage the other networks to do similar things. If it fails in the ratings, that would be a death knell for serious subject matter on television. And that would be tragic."

Author Gerald Green's orginal idea for "Holocaust" took shape years ago as a film about the artists at Thersienstadt, a model concentration camp maintained by the Nazis as amouflage for the atrocities committed at Auschwitz, Buchenwald and others. ABC was approached with Green's concept and rejected it as a "downer" that couldn't be turned into cheery entertainment. In Hollywood now, ABC staffers are spreading the word that "Holocaust" will flop because viewers don't want to be, or even risk being, depressed. If they don't, it's partly because ABC has been feeding them a steady diet of cotton candy ever since, and despite, the success of "Roots."

Incoming NBC President Fred Silverman - outgoing head of programming at ABC - has told colleagues that he thinks "Holocaust" will draw a large audience but that he would have preferred to title it "Two Families" (the film follows the sometimes overlapping destinies of a Jewish and a Nazi family) and promoted it "differenlty" than NBC is doing - presumably, playing up the melodrama, of which there is plenty, and downplaying the history.

From Stockton, Calif., where he is making a new movie, Marvin Chomsky, who directed all of "Holocaust" (actually 7 1/2 hours without commercials), says he does not think the subject matter will frighten viewers off. "'Roots' was not a fun festival, either," Chomsky says. "Soap opera has turned on human misery ever since I was a kid, and before, and it remains popular. 'Holocaust' is not one gore after another. We don't dwell constantly on misery or breast-beating. I think the moments of agony are handled truthfully."

Chomsky directed six of the 12 hours of "Roots," which was indeed watched by record millions. But "Roots" contained proven commerical elements, including scenes of sex and violence, that "Holocaust" largely lack "Roots" was set in a faraway past that distanced the material considerably and made it safer. "Holocaust" covers an era much closer to the present.

The producers and actors discovered the sensitivty of the material when they shot the film in Austria and Germany in 18 weeks last summer. In Berlin, production was disrupted by a man who threw beer bottles at the filmmakers from a balcony. In one small German town, a little old man repeatedly walked in front of the camera to shout, "I killed you Jews once and I'll kill you again." Swastikas were painted on some of the sets.Two of the first four days' shooting were lost when the processing laboratory mysteriously ruined the film, Berger said; another lab was found. Many German and Austrian techicians refused to work on the film.

Officials in Hungary, Czechoslovakia and Yugoslavia gave permission to film in those countries. Then they read the script. Permission wihtdrawn. Officials sais the scripts had "Zionists" elements, Berger was told not to bother trying to get into Poland or East Germany, either. "In the places we did shoot," he says, "the reaction ranged from complete co-operation to complete hostility."

The social importance of "Holocaust" is not in reminding the world that the Nazis were monsters. In fact, every attempt is made to humanize them, to show their pitiful as well as despicable aspects, and to wrest them from the realm of caricature, even comic caricature, into which they have fallen in movies like "The Producers" and TV series like "Hogan's Heroes."

"There are only two 'heil Hitlers" in the whole thing," Chomsky notes; that old boot-clicking Nazi stereotype may have been as glamorizing as it was stigmatizing. "Holocaust" does not aportion guilt to groups or sects or nations so much as it explores the more disturbing shades of gray, the guilt shared by all. Media-conscious religious groups and television itself, with its gospel according to whoopee, have helped create in the '70s a psychological environment that often seems hedonistically if neurotically guilt-free; that's another, reason one may fear for the drawing-power of "Holocaust" and hope that those fears will be proven wrong.

There are peripheral controversies involved with "Holocaust" as well. NBC buckled to pressure from a few affiliates and removed four seconds of decidely anti-erotic frontal nudity from the finished film, over Chomsky's protests. Half the cut footage was an actual still photograph of two women being led naked to a gas chamber. The other half was a reenactment of such a scene in which unclothed women could be glimpsed in the background.

"To me, this is like photographing a horse race and not showing the finish line," says Chomsky, "We were depicting the conclusion of the Nazi logic of total dehumanization; they were reducing the Jews to a sub-human level. This kind of thing has already been seen in documentary footage. But the affliliates cried out before any of them had even seen our film. Somebody warned them and got them very, very nervous."

Executive producer Herbert Brodkin could not dissuade NBC President Robert Mulholland from cutting the two brief scenes (there is still a considerable amount of male and female semi-nudity in the film). Producer Berger thinks the cuts are relatively unimportant.

"It's too bad the network couldn't see there was a difference between this and 'Charlie's Angels,'" he says. "This is not jigglevision; this is anything but prurient in intent. But we are talking about six feet of film out of 50,000 feet that will get on the air. And if that four seconds had given one network affiliate the excuse not to carry the show, it's worth it to cut it out."

It seems incredible that stations unruffled by the smutty shananigans of "Aspen" or "79 Park Avenue" or "The Moneychangers" would get into lathers over the fleeting nudity in "Holocaust," but station managers are notoriously jittery about controversial programming.

Partly to protect tis against possible affiliate defections over such troublesome material, and partly because "Holocaust" is a difficult program to "promote" without being too blatantly tasteless ever for TV, NBC has spent weeks lining up and circulating recommendations from civic and religious leaders.

It begins to sound like watching "Holocaust" is some kind of painful civic duty, but Green and Chomsky and a cast of true actors as opposed to guest stars have made the fictional characters tremendously dimensional and affecting against the authentic historical background. The impulse to be sanctimonious or preachy has been for the most part kept in check; "Holocaust" is more story than sermon. And yet the film's spiritual impact on the nation could be as great as that of any story television has ever told, including "Roots."

At a press conference here, Rabbi Marc Tanenbaum of the American Jewish Committee said the programm represents "an unprecedented exposure of the meaning of the holocaust to more people, potentially, than all the books and studies and curriculum ever prepared on the subject."

"I've seen the complete film three thiems." said Tanenbaum. "And each time I came away bawling like a baby. It really has a transforming power. It really could make a difference."

"Holocaust" really could make difference in television as well as a difference in public attitudes toward the holocaust and what it represents. Everyone in television will be watching next week to see how much of the nation watches this program; 1,100 families with Nielsen meters on their TV sets will in effect be casting decisive ballots on whether TV is to get better or become even worse. However they vote, the mere fact that "Holocaust" got on the air takes the wind out of the sails - at least for the moment - of all those who think there is no hope for television. There is some, after all. Come Monday more or there may be less.