As a result of his humanitarian efforts, Romero began to be noticed internationally. In February 1980, he was given an honorary doctorate by the Catholic University of Louvain.
On 23 March 1980, Romero delivered a sermon in which he called on Salvadoran soldiers, as Christians, to obey God's higher order and to stop carrying out the government's repression and violations of basic human rights.
Romero was buried in the Metropolitan Cathedral of San Salvador (Catedral Metropolitana de San Salvador). The Funeral Mass on 30 March 1980 in San Salvador was attended by more than 250,000 mourners from all over the world. Viewing this attendance as a protest, Jesuit priest John Dear has said, "Romero's funeral was the largest demonstration in Salvadoran history, some say in the history of Latin America."
The United States public's reaction to Archbishop Romero's death was symbolized through the "martyrdom of Romero" as an inspiration to end US military aid to El Salvador. In December 1980 the International Longshoremen's and Warehousemen's Union refused to deliver military equipment destined for the Salvadoran government. The leader of the union, Jim Herman, was known as a supporter of Romero and denounced his death. On 24 March 1984 a protest was held in Los Angeles, California where around 3,000 people, organized by 20 November Coalition, protested US intervention in El Salvador, using the anniversary of the Archbishop's death and his face as a symbol. On 24 March, 1990 10,000 people marched in front of the White House to denounce the military aid that was still flowing from the United States to the El Salvadoran government. Protestors carried a bust of the archbishop and quoted some of his speeches, in addition to the event being held on the anniversary of his death. Noted figures Ed Asner and Jennifer Casolo participated in the event.
On 25 March 1980 US Secretary of State Cyrus Vance revealed that the White House would continue to fund the Revolutionary Government Junta and provide military aid to them, in spite of the pleas of Oscar Romero and his death immediately prior to this announcement. On 31 March 1983 Roberto D’Aubuisson was allowed entry to the United States by the State Department after deeming him not barred from entry any longer. When asked about D'Aubuisson's association with the assassination of Archbishop Romero, the State Department responded that "the allegations have not been substantiated." In November 1993, documents by the State Department, Defense Department, and the Central Intelligence Agency were released after pressure by Congress increased. The 12,000 documents revealed that the administrations of President Reagan and President Bush knew of the assassinations conducted by Roberto D'Aubuisson, including that of Oscar Romero, and still worked with him despite this.