2123 was from Novels.
Don't scare me like that!
PICARD: But the Prytt are not. They are reclusive to the point of xenophobia.
CRUSHER: Well, think about Earth. What if one of the old nation states, say Australia, had decided not to join the World Government in twenty one fifty? Would that have disqualified us as a Federation member?
PICARD: That analogy is not exactly
Australia wasn't a problem. Crusher was constructing a hypothetical and pulled Australia out of of her ass.
(But what Australia was doing up her ass, I will never know.)
A lot of people missquote or remember that line badly, including whosoever was making up this claptrap abut 2123. From what Crusher said there is no reason to believe that all of Earth didn't unify in 2150 or that there was any staggering at all, in fact from how she phrased it there can't have been any staggering.