To one who turns the pages of your history and reflects upon the causes of what has been accomplished it is apparent that the triumphal progress of Divine religion has contributed in no small degree to the glory and prosperity which your country now enjoys. It is indeed true that religion has its laws and institutions for eternal happiness but It is also undeniable that it dowers life here below with so many benefits that it could do no more even if the principal reason for its existence were to make men happy during the brief span of their earthly life.
Pius XII, SERTUM LAETITIAE (1939)
The first papal visit to the United States is usually thought to be that of Pope Paul VI in 1965. However, Cardinal Pacelli, the future Pius XII, visited the United States in October-November 1936, becoming the first man who served as pope to set foot in the land of the free and the home of the brave. As Papal Secretary of State, foreign travel came as part of the job, but the purpose behind his visit is still something of a mystery. Some historians have claimed that he struck a deal with FDR by which the United States would establish diplomatic relations with the Vatican in exchange for the Church silencing radio priest Father Coughlin, initially a supporter of FDR but by 1936 a fierce critic.
It was usual for Pacelli to take an annual vacation and he changed plans to visit Switzerland for the United States on short notice. He met with FDR on November 5, the day after his re-election. He did secure a promise that he would appoint a personal representative from him to the Vatican, although this promise was not fulfilled until 1939, after Pacelli was elected Pope.
Pacelli never met with Father Coughlin. During his tour of the US, Pacelli brushed aside questions about Coughlin from newspaper reporters, although he made it clear that the Vatican did not agree with his criticisms of Roosevelt.
After the election Coughlin did cease broadcasting briefly, although he returned to the radio in 1937. As for Pacelli, he came away with a keen perception of both the strengths and weaknesses of the Church in the US. His comments in Sertum Laetitiae, issued in 1939 on the one hundred and fiftieth anniversary of the establishment of the US hierarchy, now seem prophetic. Go here to read it.