The loss of the Expanse will certainly have repercussions we can't even begin to imagine. The fact that in the alternative 26th century, it covers 1/4 of the galaxy, surely affected every aspect of life (both in and out of the Federation). The fact that the last 400 years have been erased from history is going to wipe the slate clean, as it were. Whatever the Federation is like in that version of the 26th century, the fact that the Expanse essentially never existed is going to result in a whole new version of events.
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. Daniels had to make sure Archer WOULD act - to ensure that this version of the future never happened. Which, as we know now, it won't.