The loss of the Expanse will certainly have repercussions we can't even begin to imagine
Daniels can 'imagine' the repercussions just fine.
The reason why Daniels took Archer to see that version of the future is to show him what would happen if he failed to act.
Almost certainly NOT the scenarists' intent; if that was the scenarists'/Daniels' intent, they gave absolutely no sign of it. Plus, humanity wold be extinct in an 'Archer failed to act' timeline.
More in line with what was shown - Archer changed history, but not in any significant way for the federation.
Daniels was aware and had no problem with the change.
AND - Talking about 'zero hour' - Daniels reiterates 'dozens, eventually hundreds of species'. And he was pretty adamant about Archer's specific role in federation
Hundreds of species remains the norm. Meaning, by the 24th century, the federation maxes out