The best answer I heard to the TP question (and hoarding) is that in a crisis, people typically choose one thing they know they can control and then overdo that thing. It's largely cultural. So in the US, it was TP.
At the same time, our household consists of two busy (usually overworked) professionals, so we always stock up on toilet paper. Our goal is to go to the store just once a month, always.
So we already had quite a bit of TP. We have it on subscribe and save on Amazon and it comes every three months (again, trying to cut down on the number of trips someone else has to make in a vehicle).
I was able to get a bunch of those cheap paper napkins from InstaCart two weeks ago. If this goes on into July, though - we are going to have to look through the book collection pretty carefully. The books with thin pages are mostly old and precious, so dunno what we'll do. We do have a handheld shower right next to the toilet, though - as most Europeans do (or they have a bidet).
Save your squirt bottles. Get or improvise a shower cap if your hairstyle is an issue, because a quick shower is way nicer to me than using rags or pages from books.
WHY we would continue to have a TP shortage, though, I have no clue. Surely people will not continue to buy 10X as much TP for the rest of all American history?