Ah that's right, I forgot about what a hassle it is to change accounts on the Vita.
Actually it isn't a hassle at all. This could be new, but when I restored my backup today it also restored all my wallpapers, bubbles and settings.
So all you have to do is:
1. Back up current memory card.
2. Completely reset the Vita.
3. Login with US/EU/JP/HK account and restore the appropriate backup.
You can also skip the intro video by restarting the Vita.