Having discussed it, the mods (Wes, Hooman, and I) reckoned that the alliance should still be in effect, as other players probably went through the late '20s with that assumption.
That said, the treaty text itself was never posted, so we're suggesting that its duration be ten years, or a year after a signatory gives notice that it's out, whichever is the later. Thus a signatory could provide notice by 7 July 1930, and the treaty would end on 7 July 1931, a decade after it was signed. This should allow the treaty to be ended soon without requiring anybody to break their oath or such.
With the 1921 war now sorted out, I see no reason "the locals" can't write about Argentina in storylines, so long as they bear in mind that Nordmark, SAE, and Italy may take more than a passive interest in what happens. But really, that goes for most NPCs in the world anyway.
If it's considered necessary, I can look at putting together a quick report on 1922-1930 Argentina to clarify military power and diplomatic policy.
Thoughts?