High Sierra removes Google Talk support for Messages. That's not really Apple's fault, as Google is migrating all Google Talk functionality to Hangouts and doesn't allow third-party clients to connect to Hangouts. But after upgrading from Sierra on a machine that was logged in to a Google Talk account, Messages is still connected to that account and receives messages but can't send them. How can I log Messages out of this account which is now useless? It doesn't show in the Accounts tab of the Messages preferences.
This might help https://apple.stackexchange.com/a/107120.
I would do the different steps and then start from scratch. Or... you might try checking what each file in those directories do and see if yo can delete the account manually.
If you try the each file method, it appears that the file
~/Library/Preferences/com.apple.iChat.Jabber.plist contains the Google Accounts. If you see your account delete it and relaunch Messages.
Important: Please backup your files before doing something that might harm your OS. ALWAYS. I've learned this the hard way. It's always easier to copy back files than to have to fix something from scratch.
I upgraded to High Sierra and found that my Google Talk account stopped receiving messages automatically (fixed in newer version maybe?), so not sure if this works, but I have a couple suggestions:
1) Try removing your Google account from Internet Accounts completely and making sure that you don't keep receiving messages.
2) If that's not enough, open Keychain Access and do a search for keys with the name Google in them. You can view and copy the passwords and info to a text file if you would like a backup. Delete any that you find.
After you do either of those, make sure to go to Internet Accounts and either add it back or re-enter the password for your Google account. Hope this works for you!