According to
this your past purchases will be transferred when you change countries, but I'm also assuming only the titles available to that country would be brought over.
It also says your Kindle Unlimited will be automatically deactivated and all the KU books you have currently will be automatically returned.
You also have to have an address for the new country you're changing your region to. Which might be the easiest part.
It all sounds like a headache to me, tbh.