A BOMB WENT OFF a month ago in a hotel restaurant in the village of Comber in Northern Ireland. The bomb contained gasoline carefully mixed with some sticky substance to make it adhere to the skin. It killed 12 people, some of them children, some burned so badly that could be identified only by their dental charts. The Irish Republican Army announced that it had planted the bomb. It was one of more than 200 bombings by the IRA this winter in Northern Ireland.

Unhappily, there is a degree of American responsibility for this campaign of terrorism. Some of the money that buys the explosives, and sustains the bombers, is still coming from the United States. It is contributed by people who remember a very different IRA of two generations ago. This support arises from a confused sentimentality, one example of which, we regret to say, was printed in The Washington Post Magazine of March 12. The article was engagingly entitled, "Not Every Man Was Born With a Boat to Catch," but the reader is entitled to know a bit more about a couple of the organizations described in it.

The Irish Northern Aid Committee claims to be raising money only for the families of "political prisoners" in Northern Ireland. There is every reason to think that the money goes, in fact, to the IRA. Quite true, no one has direct evidence of it. The money is transmitted in cash, by couriers. But the Northern Aid Committee provides no accounting of its benevolences. No one seems to be able to find any families aided by it, in Northern Ireland or anywhere else. And a succession of people who are members of the committee have been convicted, in American courts, of gun-running.

Then there's the Irish National Caucus, active here in Washington, which calls itself merely a lobby for Irish unity.Not everyone shares that view of it. The prime minister of the Irish Republic, John Lynch, wrote last month that the Caucus, "whatever its recent protestation to the contrary, has been closely associated with the cause of violence in Northern Ireland."

The IRA myth is that it is carrying on the struggle to eject the British Army from Northern Ireland and unite it with the Republic. The reality is, of course, that Northern Ireland remained outside the Republic because two-thirds of its population are Protestant and bitterly hostile to Irish nationalism. The Protestant paramilitary organizations are fully as vengeful and violent as the IRA, and they have more men. The IRA's strategy is to incite a civil war into which the Irish Republic would be drawn. Its tactics have long since degenerated into random terrorism, like the bombing at Comber. The vast majority of its victims have been Irish civilians, of both religions and all ages.

A year ago four American political leaders of Irish descent celebrated St. Patrick's Day with a courageous message calling for an end to this violence, and appealing to Americans to renounce all support for it. On St. Patrick's Day this year the four - Sens. Edward M. Kennedy (D-Mass.) and Daniel Patrick Moynihan (D-N.Y.), House Speaker Thomas P. O'Neil Jr. (D-Mass.), and Gov. Hugh Carey (D-N.Y,) - were joined by 18 more senators, congressmen and governors in repeating their message: "We are deeply concerned over reports that some individuals, organizations and groups in the United States are still providing assistance to enemies of peace in Northern Ireland. There is no justification whatever for any persons to lend their support or good names to activities that enhance the cause of violence . . . The season of St. Patrick's Day brings the green of spring, the ancient sign of hope and rebirth . . . In this spirit we make our appeal, hopeful that it will touch responsive chords in the hearts and minds of all who truly seek an end to the violence in Northern Ireland.