It was a sleeper in the flood of changes that poured from the Second Vatican Council nearly 25 years ago, but the call to create national conferences of bishops profoundly changed American Catholicism.

The establishment of the National Conference of Catholic Bishops in 1965 has transformed the American hierarchy from an ecclesiastical star system, in which two or three powerful prelates spoke for the church, into a collegial, consultative team that works from a consensus of some 330 bishops.

Nowhere is the change more dramatic than in the church's stance toward war and peace.

"My country right or wrong, my country," said New York's powerful Cardinal Francis Spellman of America's involvement in the Vietnam war. His stature was such that he was widely perceived as speaking for American Catholics, and certainly for the hierarchy.

Less than two decades later, a lowly antiwar auxiliary bishop from Detroit, the Most Rev. Thomas J. Gumbleton, made a short speech at the annual meeting of the bishops' conference and set in motion a process that would end with the entire body of bishops challenging the nation's nuclear defense policy.

Appointed by the pope as successors to the apostles and answerable only to Rome, bishops are obliged to teach the doctrine, provide for the sacraments for the faithful and administer the church in their assigned territory. But the bishops' conference has been the channel through which they have had their greatest impact on the nation, Catholics and non-Catholics alike.

Their efforts to apply Christian precepts to such urgent and complex problems as nuclear warfare and economic justice greatly enhanced the hierarchy's credibility and stature even among those who disagreed with their conclusions. Some observers believe they have been influential in their staunch opposition to American military intervention in Central America.

In contrast to the autocracy of traditional Catholicism, the bishops' conference functions with the democratic principles of a rotating elected leadership with which the bishops, as Americans, are comfortable. It is strictly one-man, one-vote, and rank has no privilege, as the late Cardinal Terence Cooke discovered some years ago when he attempted to address the body without following procedure.

"You are out of order," said the presiding officer, an archbishop. There were gasps, but Cooke took his seat.

In selecting their leaders, the bishops have been concerned with finding men attuned to American Catholicism rather than those with ecclesiastical rank or in favor with Rome. Not since 1972 have they chosen a cardinal.

Last November, Cardinal Bernard Law of Boston, perceived to have particularly close Vatican ties, was defeated for the presidency and vice-presidency of the conference and in six separate ballots for other positions.

While the American bishops almost always have chosen liberal or progressive presidents, the choice is less a matter of ideology than collegiality, said Jesuit author, the Rev. Tom Reese.

On the peace pastoral, he points out, New York Cardinal John J. O'Connor, who was in the opposition on the drafting committee, "fought like hell for his point of view, but once he lost, he signed on" to the finished document, Reese said. "He's a team player."