Overall, 45 percent of Protestants and 47 percent of "other Christians" thought the war was a mistake. The figure was 52 percent among Catholics, 58 percent among other religions and 62 percent among those who had no religion.
Frequency of church attendance also held sway. Overall, among those who never went to church, 62 percent said the war was a mistake. Among those who attended services once a week, the figure was 44 percent.
In describing the official positions of churches, though, they get the story wrong.
The World Council of Churches, the U.S. Conference of Catholic Bishops, the Vatican and the Church of England were among those that characterized the conflict as unjust, and urged diplomatic alternatives.
The Vatican & USCCB certainly opposed the war and urged diplomatic alternatives, but at no time did either say the war was "unjust" (though certain individual prelates certainly did). You may not care, but in Catholic social teaching it makes a difference. If you say a thing is unjust, you have an obligation in justice and charity to undo the injustice and to the extent possible restore the status quo ante.