Why TF would they use XRP when they already have a shitcoin they control called USD?
Discussion
Your question I think has merit for someone who understands money but I'd guess if they were to bring it in then they would engineer some crisis and then say that XRP is the solution -most people wont realise its a recreation of fist on digital rails. One advantage over current USD for XRP is just the digital tails. I assume that would actually represent an improvement from USD to XRP. The supply side still sucks but it's on digital rails.
Have you not heard of tether? The dollar is already digital.