First just because it once existed doesn't mean it still does.
Ever hear of Occam's Razor?
Like I keep saying: It literally does not make any sense for there to be no Earth government. If there was not one, then Earth citizens would have no representation in the Federation - therefore, they would have no rights. That sound right to you?
And there is nothing so magical about the Federation that would cause member worlds' governments to vanish when they join. There's no reason they would do that. It's inconceivable that the Federation would make such a demand. No world would ever want to join if it meant they would lose their own local government! Then the Federation really would be no better than the Borg.
But I don't think after ENT we have any evidence of a local Earth Government that has say on External Security issues that face earth.
We don't have any evidence of a lack of one, either.
And, non-canon though it may be, the novels have fully developed the structure of United Earth government, and they are of course the only way we are ever going to see any more stories taking place in the prime (non-Abrams) timeline, so their word is as good as canon.