They've been being pretty whacky over the last few years "oh no a women's in charge sometimes, so lets schism" and "we made a sensible choice of pope last time, so lets put this complete ass in charge this time".

Honestly "the anti-christ has arrived and it's this random American" isn't much more strange.

Does it count if a bishop, archbishop, or pope calls him "an" antichrist? Or do they have to use the definite article "the"?

Context: in traditional Christian theology, there isn't really a strong current of talking about "the" antichrist - there's plenty of precedent for talking about antichrists, plural, though. The idea of putting emphasis on a specific "the" antichrist is more of a modern premillenial dispensationalist thing. Not something you couldn't see pop up in Catholic circles I suppose, but it wouldn't be native to them.

'an' Antichrist will be sufficient