First American pope elected and will be known as Pope Leo XIV

Will he be taxed on his foreign Papal salary? Or will he forego the salary , like Francis did?

Apparently heads of foreign states are exempt.

What's your source on that, at least in the case when the head of the foreign state also remains a US citizen?

There's also the interesting question of whether he will remain a US citizen after all, or whether taking the office of pope will count as him relinquishing US citizenship under INA §349(a)(4): https://travel.state.gov/content/travel/en/legal/visa-law0/L... In the latter case, the tax question would not arise.

Existing US Department of State policy applies an administrative presumption to most cases of accepting foreign government employment that the person does not intend to relinquish US citizenship unless they affirmatively state otherwise, but they don't apply any such presumption to becoming a foreign head of state or a foreign head of government. They actively analyze such cases individually with no default presumption.

Pope Leo XIV will lose his US citizenship due to his acceptance of the papacy if and only if he intended to relinquish US citizenship by that act, based on the standard of proof of the preponderance of the evidence (the same as in civil lawsuits). He has the right to dispute the question in court if he and the US Department of State disagree on the answer, but I imagine this would in practice be handled more quietly for such a high-profile case.

There is no way in hell they'd revoke his American citizenship. American Catholics would be up in arms.

He might want to himself for tax purposes alone. I don't know how much the standard salary for a pope is, but I'm pretty sure it's above the threshold for the US "give us your foreign earned money" tax law.