The AFAIK is the thing, though; if there's doubt there's possibility.
Plus, I haven't seen the episode in question, but even if it was later assignation of importance, the signing in question still needed to have happened for those people to give it said importance, so stopping it probably would have had Consequences, right?
The confederacy or nazis having won in changed timeline stuff is cheap and rubbish imho because it only technically results in the oppression of people who've really had enough of that sort of thing already. The story becomes at their expense, really, and not even their focussed-on expense. The oppression of me in the background is something I would object to quite heartily (that throwaway 'women, working? hahahaaa!' pretty much made me think OH WHAT IS THE POINT HERE?). Ro-Boy, how witty. Witty like a poke in the eye.