In 1862, Abraham Lincoln called the relationship between the United States and the Roman Church “pleasant and beneficient.”
“It is believed that ever since the tide of emigration set in upon this continent the head of the Roman Church and States has freely recognized and favored the development of this principle of political freedom on the part of the Catholics in this country, while he has never lost an opportunity to express his satisfaction with the growth, prosperity and progress of the American people.
It was under these circumstances that this Government, in 1848, wisely determined that while it maintained representatives in the capitals of every other civilized state, and even at the capitals of many semi-civilized states which reject the whole Christian religion, it was neither wise nor necessary to exclude Rome from the circle of our diplomatic intercourse.”
2 years later, the United States would end all diplomatic relations with the Holy See.
Why? Rumors of a Catholic implication in his assassination.
The last straw was false reporting in the New York Times that Pope Pius X forced the protestant members of the US Ambassadorship outside the walls of Rome to celebrate their religious services.
One of the US protestants in Rome said however: “I beg to say that there is no truth in either statement.”
“The American Protestant church in Rome remains where it was located at the commencement of the season, and will not, I think, be interfered with, for the present, at any rate.”
Never-the-less, it led to the US Congress withdrawing all funding for the US Ambassador in Rome, de facto ending diplomatic relations with the Holy See in 1867.
“It is provided that ‘no money hereby or otherwise appropriated shall be paid for the support of an American legation at Rome, and from and after the thirtieth day of June, eighteen hundred and sixty-seven.’”
For the next 117 years, the two countries had no official diplomatic relations. Pope Pius X even refused a meeting with Teddy Roosevelt.
Occasionally, presidents would send personal envoys to visit the Holy See for discussions of international humanitarian and political issues or visit themselves with their First Ladies.
However, until JFK, the Vatican was largely accused of being anti-American in the US.
On January 10th, 1984 the United States and the Holy See announced the re-establishment of diplomatic relations to little opposition from anyone. Ronald Reagan and Pope Saint John Paul II were said to be especially close because of their ant-communism and interest in Polish independence from the USSR.