Since Pope Leo XIV is now the head of state of a foreign nation, will he lose his US citizenship?

Perhaps. I’m not an expert there and can’t really weigh in. But I can shed some light on a much more pressing question: If Pope Leo XIV loses his US citizenship, would he be able to get an O-1A visa?

The O-1A visa is for “aliens of extraordinary ability” – people who are at the top of their field globally. USCIS judges whether you are “extraordinary” enough using 8 criteria of which you must meet at least 3.

Let’s see how Pope Leo XIV stacks up against the 8 criteria:

Membership: Prior to becoming Pope, Leo was selected as a Cardinal of the Catholic Church. While perhaps an unusual way to meet this criteria, one could make a strong case that the College of Cardinals is an exclusive professional organization.

Authorship: Leo has a PhD in Cannon Law, and has published a thesis, a book, and likely some peer-reviewed papers. So it should be pretty straightforward to argue he meets the authorship criteria.

Judging the works of others might be more tenuous. To meet this criteria you must show that you were in a position to judge experts in your field. Although – as a priest – Leo has been vested by Christ with power to “forgive” and “retain” sins (John 20:23), it would be hard to argue to USCIS that hearing confessions counts as judging. Perhaps in his academic career Leo acted as a peer reviewer – which would be a more straightforward way to meet the judging criteria. So this is a maybe.

Publications (press): Obviously, Leo has been mentioned by name in major publications around the world. Slam dunk here.

Critical role in a distinguished organization: In order to make this argument, we would have to prove two things: One is that Leo has a critical role at an organization, and two that the organization is distinguished.

As Bishop of Rome, Vicar of Christ, and Supreme Pontiff of the Universal Church, Leo clearly has a critical role in the Church.
The Roman Catholic Church is millenia old, and holds the “Keys of the kingdom” of Heaven (Catechism, 551). Luckily USCIS does not require that an organization's record be spotless, so there shouldn’t be a problem here.

High salary: A quick Google search reveals that Cardinals typically earn under 60k per year, so it’s unlikely that Leo meets this criteria.

Internationally recognized prizes: You could try to make a creative argument here about him being “awarded” his cardinalship or the Papacy. But again this likely wouldn't be the strongest argument.

Original Contribution: To meet this criteria, we must show that Leo made an original contribution in his field, and that this contribution had major significance. I imagine with enough digging we could prove that he made significant contributions during his missionary work in Peru.

But it’s not really necessary, because we can already make a very strong case for Leo based on Membership, Authorship, Press, and Critical Role.

But there is one critical problem with Pope Leo’s hypothetical O-1A application: The O-1A is an employment-based visa, and so is only available for people working and living in the US.

So unless he intends to move the papal seat to the Windy City, I would not recommend Pope Leo XIV apply for an O-1A visa.

IF he loses his US citizenship, Leo will be better off applying for a diplomatic “A” visa when he makes trips to the US.

All opinions my own.