WE HAVE seen it before and we are apt to see it again. The Provisional Irish Republican Army (IRA) explodes a bomb in a mall or on a crowded street. Within an hour, American television viewers see shrouded corpses, ambulances speeding away with the luckier victims and interviews with uncomprehending survivors.

When other terrorists around the world cause the same sort of carnage, American politicians and media are quick to assail those who back them with money and propaganda. Not so with the IRA. This is strange. It would be so easy. One of the IRA's sources of support is not in some exotic hideaway, after all, but right here in the Bronx.

It is called the Irish Northern Aid Committee (Noraid). It was convicted of violating the Foreign Agents Registration Act in 1981 by U.S. District Court Judge Charles S. Haight for failing to list the IRA as its principal foreign agent.

Who does Noraid aid? Fundraising letters sent out in 1971 and 1972 said: "Our support goes exclusively to the Provisional IRA and those who are working with them." Where does the money go? "Our funds are channelled through Joe Cahill of Belfast to be used for the advancement of the campaign in Northern Ireland." What is the relationship between the IRA and Noraid? "We are fighting a guerrilla war and will continue to do so. We, the members of the Provisional Irish Republican Army, will fight and die until victory is ours. Remember, the Irish Northern Aid Committee is the only organization in America that supports the Provisional IRA."

Asked recently if Noraid sends money and guns to the IRA, Martin Galvin, Noraid's publicity director, responded: "That's absolutely untrue. We raise money for the families of Irish political prisoners."

Even so, this support frees IRA money that might otherwise go to those families.

Joe Cahill, arrested in 1973 in Ireland aboard an IRA ship carrying five tons of weapons from fellow terrorists in Libya, is a convicted gunrunner and was sentenced to three years in prison. He has also served as joint treasurer of the IRA's political arm, the Sinn Fein, and held a high rank on its ruling "Army Council."

Michael Flannery, the 84-year-old co-founder of Noraid, was arrested in 1981 on federal charges of conspiring to ship arms to the IRA -- the arms in question being a 20-mm cannon, 47 machineguns, a flamethrower and numerous rifles -- but he was acquitted when he claimed the CIA had led him to believe he was cooperating in an undercover operation. Even though the CIA vigoriously denied any involvement, the jury believed Flannery. A Noraid spokesman denies any connection between Noraid and these activities. Martin Galvin, Noraid's publicity director, said, "The money came to Flannery from sources outside of Irish Northern Aid {Noraid} who specifically wanted to aid the IRA militarily."

According to the British Home Office, Galvin "went beyond what was acceptable behavior by a foreign visitor" when he went to Northern Ireland in April 1984 and gave a speech praising the IRA for soaking a young private in the British army in gasoline, burning him alive and then riddling his body with bullets. As a result, Galvin was banned from Ulster.

While we bitterly condemn Middle Eastern states that fund Palestinian terrorists and urge the Europeans to abandon lucrative economic links with Libya, Syria, Americans continue to support the IRA. Noraid says these donations support Irish "widows and orphans" and the families of "political prisoners" oppressed by Britain's "colonial rule" of Northern Ireland.

At Noraid dinner-dances and testimonial dinners, fund-raisers exploit the desire of Irish-Americans to identify with their roots in the "old country." Creating an atmosphere of sentimentality and reminding the audience of their responsibilities to their less fortunate former countrymen triggers the flow of contributions.

A former official on the State Department's Irish desk, Sarah Horsey, says: "Most Americans simply do not know what goes on over there. What Noraid contributors know about Ireland seems to derive from hazy folk memories of the potato famine and the brutality of the British during the 1919 revolution."

Noraid's congressional district in the Bronx is represented in Congress by Rep. Mario Biaggi, the founder and chairman of the Ad Hoc Congressional Committee for Irish affairs. Biaggi maintains that he formed the committee at the request of the Ancient Order of Hibernians -- one of the groups that picked Michael Flannery as grand marshal of the 1983 St. Patrick's Day parade.

One bill Biaggi proposed (H.R. 2597) demanded British withdrawal and immediate unification with the Republic of Ireland as conditions for $500 million of economic aid to Northern Ireland.

Why does Biaggi, who represents the predominantly Italian neighborhood that also includes Noraid's national headquarters, feel so passionately about Northern Ireland? Bob Blancato, a Biaggi aide, said Biaggi had first become "educated" about Northern Ireland from fellow officers in the New York City Police Department. Biaggi has traveled to Northern Ireland and met with Sinn Fein representatives, prompting the then prime minister of Ireland, John Lynch, to write in a letter to Biaggi: "We in Ireland have noticed your public identification here with supporters of violence." Blancato takes the position that the Sinn Fein has "no connection to the IRA."

According to a British Foreign Office policy statement, the Sinn Fein's political platform calls for "a rigid socialist program, involving full nationalization, state control of the export and import of capital and limits on property ownership -- 'We deny the right to personal ownership of productive property such as a large farm or a large factory.'"

Despite evidence that Noraid, Sinn Fein and the IRA are exploiting American ignorance and Irish-American nostalgia to work against the interests of the United States, no one holds this powerful American support group to account. Cahill, Flannery, Galvin and their associates in Noraid remain practically unknown in America. Our reluctance to confront or even acknowledge that donations to Noraid bankroll the IRA is a moral tragedy. T. K. Jones is a free-lance journalist in Oregon.