I doubt many are Catholic. J.D. Vance would be an option, tho.
https://soldiersangels.org/the-diversity-of-our-service-memb...
History is why catholics are at 20%. Which is a significant force and a dangerous game to alienate them.
At this point I don't think anything other than the church retains the ability to present a coherent moral or metaphysical intellectual framework to people who care about that kind of thing.
I would be very surprised if the united states is not majority catholic in ~100 years
More likely he would just assert that the Pope isn't actually the Pope, and thus any excommunications are void, and his supporters would roll with it. Some of them already believe this. Any words, true or false, which make them feel better to believe. That's religion, right? He is their true religion.