Incorrect IP Geolocation

My residential public IPv4 address is incorrectly geolocated ... I have submitted requests to Google and MaxMind to have the IP/Geolocation data base fixed.  ...

That's pretty much all you can do. Comcast/Xfinity assigns your public IP address, but does not control where others think that IP is located. That's done by third parties.

... Is there anything Xfinity can do to help speed up the process?

They can, but they won't. That would cost them a few pennies. The key phrase in https://www.xfinity.com/support/articles/correct-geolocation-data is:

If your geolocation is configured incorrectly, you’ll need to contact either the website you’re experiencing issues on, or the geolocation services themselves.

Whenever it can, Comcast/Xfinity throws the responsibility for fixing things back onto its customers.

@DeltaOne 

I'll add, if I may, to @BruceW 's great info. If you are using a router that has a MAC address cloning feature, you can clone a different MAC address into it. This will force a change of your Comcast assigned WAN / public IP address. No guarantees that the new address won't also have incorrect geo-data as it may be from the same block of IP's. YMMV.

BruceW and EG: thanks for the comments and information.

I have heard back from MaxMind saying the fix will be in the database within two days.