Pope John Paul II turned Catholic teaching on its head when he declared that it was a moral obligation to provide food and water indefinitely, even to patients in a vegetative state with no hope of recovery. “The administration of water and food, even when provided by artificial means, always represents a natural means of preserving life, not a medical act,” he said at an international conference last March.
Admittedly my understanding of Catholic church teachings is pretty limited but, as I understand it, if the Pope slipped into a coma or had an aneurism or a stroke and became mentally incapacitated for some reason after his feeding tube was inserted, and unless he makes some sort of prior arrangements, he’s still the Pope…… and his current instruction is that the tube stays - indefinitely.
If that came to pass who would lead the Catholic church? I assume that he is tasked with absolving the upper-upper level of the church hierarchy, who have in turn absolved those lower in the hierarchy - if he can’t, who can? Where does that leave the whole process? I had to ask a former Catholic about this but it appears that he either has to resign or pass away? Where would that leave the Catholic church?
– and possibly more importantly, where does that leave the millions and millions of Catholics with living wills who have made their wishes legal and clear, and those wishes are against what the Pope has said? In hell?

I’m guessing that the College of Cardinals would run the Vatican and the Church. There may even be some provision for replacing an incapacitated Pope.
As to the question in the last paragraph, I dunno. I’m guessing most American Catholics will do what they have done about birth control - ignore the Vatican’s edicts.