Hi, @IndigoMelody. Are you asking about changing the region for where the CDN node is or is this the region for Functions?
For the CDN nodes that serve the site, this should already be happening. We have CDN nodes in many locations around the world and mutiple nodes in each location (in nearly all cases).
If the site is not being served from different location, please let us know what custom domain this is not working for and we will be happy to share instructions to resolve it.
If this is about the Functions region, that can be changed. If this is the issue, please let us know which site this is for and what region the Functions should be deployed in. Once that is done, a new deploy of the function (something that changes the bundle checksum) is required for the change to take effect.
If there are questions about any of this, please let us know.