Who ever could have guessed that the election of the first American pope would cause political problems at home?

From the moment that Robert Francis Prevost became Pope Leo XIV last year, a clash between Rome and Washington was inevitable.

Not least because, for years now, consecutive leaders of the Catholic Church have had policies that fly against the policies not just of the US government but any sensible government.

For example, it is hard to find any figure in the world more in favor of open borders than the various men who have held the office of pope in recent years. Pope Leo, like his predecessor Pope Francis, is very eager to speak up for the plight of illegal migrants. But — again like his predecessor — he is silent on the challenges that such migrants bring to the populations expected to absorb them.

Pope Leo has already pointedly announced that he intends to spend July 4 this year on the Italian island of Lampedusa. For years that Mediterranean island — with only 6,000 people — has been one of the main landing spots for illegal migrant boats heading into Europe. Pope Leo’s predecessor also visited the island. And each time the visit is in order to stress the need for the developed world to be “open-hearted,” “welcoming” and much more.

I suppose it is part of the job of a pope to stress the need for kindness.

But it hasn’t helped quell the problems that millions of illegal migrants bring into Lampedusa, Italy and then all of Europe. Whenever a portion of these illegal migrants get involved in criminal activity, including terrorism, you won’t see the pope accepting any blame for it.

But this is just one thing that would inevitably cause friction with an administration in Washington, which was in large part elected to sort out America’s illegal immigration crisis. This week the president, vice president and the US border czar, Tom Homan, have all been dragged into this battle with the pope.

The other issue that has set Rome and Washington against each other is the war in Iran. Over the past week, the pope has made a set of increasingly pointed comments. First he seemed to condemn the war by saying that “God does not bless any conflict” — a statement that many of his predecessors famously disagreed with.

Then yesterday in a speech, he added: “Woe to those who manipulate religion and the very name of God for their own military, economic, and political gain, dragging that which is sacred into darkness and filth.”

We can safely assume that this message was directed at the Trump administration more than it was directed at whoever is running the Iranian revolutionary government these days.

Of course all of this has put Vice President JD Vance in an especially uncomfortable position. As a convert to Catholicism, he cannot say as easily as Trump did yesterday, “I have a right to disagree with the pope.”

Fortunately for the vice president, there is plenty of space for disagreement, even for a Catholic.

One of the most consequential lines in all of scripture is the response that Jesus gave when asked about whether it was right to pay taxes to Rome: “Render to Caesar the things that are Caesar’s, and to God the things that are God’s.”

That single line is the fundamental basis for the whole idea of the separation of church and state. It is the basis on which this republic’s founders were able to separate religion and government. And it is something we almost take for granted.

Other civilizations don’t have such a separation. Any separation of mosque and state, for instance, is made immeasurably harder by the absence of any similar sentiment in Islamic scriptures.

And yet for the separation to work, it relies on it being respected by both sides.

It would be wrong for a US president or other Western leader to start opining on what the church should teach. For instance, if a US president were to demand that the Catholic Church start accepting women as priests, a pope would be perfectly within his rights to say, “Hey, get off my turf.” Or words to that effect.

But in the same way, there are issues of state on which popes should be very careful about treading.

Not just because a religious leader should be above such things, but because to intervene in politics makes a pope open to all the criticisms that involvement in politics must bring.

In recent days, many people have noted how rare it is to hear a pope or other Christian leader speak up for the persecuted churches in the Islamic world. Some people will remember that when Pope Benedict made a single reference to Islam in one speech, there were murders and attacks on Christians across Africa and the Middle East.

It seems that the leaders of the Catholic Church learned from the episode that it is far easier to criticize Western governments than it is to raise the slightest complaint against countries like Pakistan, where people who convert to Christianity face persecution and even death. If the church is going to play politics, it should at least be consistent.

The truth is that the relationship between church and state works at its best when its footing is mutually understood. It is a good thing that the head of the church stresses the importance of human mercy. But any functioning government or country has other things to consider.

Contrary to what this pope has recently said, there is such a thing as a just war.

Just as there are such things as borders.

It was probably inevitable that these current papal-presidential hostilities would break out. But it is a war that neither side can win.

Because the battle between church and state is like the battle between heart and head.

Neither should ever win out completely.

A religious leader may focus on the heart.

But a president — and a country — needs to keep its head about it too.