All fame after the merge was reduced to zero. If you don't have enough civ fame to become a citizen then that option will not be there, There is always the option to curse the civilization ( renounce your citizenship) in order to get negative fame with that civ, which is what those who wish to be marauders do.
You didn't state how much fame you had with the civilization.
You didn't state how much fame you had with the civilization.