Argentinian-brazilian war in 1936?

First of all, 1936 was the year that FDR made his south american tour, even meeting personally president Vargas of Brazil, before proceding to Argentina:

rafael-franco.jpg

So, in 1936 Rafael Franco took over paraguay on the February revolution (that was a coup tbh), he was a hero of the Chaco war, and tried to emulate the labourist policies made in Brazil by president Vargas, he even earned the nickname as "the paraguayan Vargas", and this caused suspicions on the argentinian government, since now both Uruguay and Paraguay had brazilian inclined governments. The 1930s were also when Brazil was surpassing Argentina as the main power in south america, and so the argentinian government was feeling more and more weaker and isolated, under the junta of Augustin P. Justo and so they cogitated to invade Paraguay and depose Franco, replacing him with a pro Argentina dictatorship. In OTL this was dismissed by Justo as anti brazilian paranoya, since there was no hard proof that Brazil and paraguay would ally themselves, and so the invasion plans were scrapped. In 1937 Franco was couped and the situation normalized.

But let's say that just after the FDR pan american tour, Franco decided to make a state visit to Brazil, and this prompted Argentina to invade paraguay and Brazil reacted by declaring war on Argentina, how would the US respond? And how would the war develop?

According to Wikipedia, Franco had bought a lot of foreign equipment before he was couped, but only a fraction of it arrived before he was removed and the order cancelled, take a look:
  • 20 FIAT C.R.32 c (only 5 were purchased)
  • 4 FIAT C.R.30B (2 were purchased)
  • 4 Breda Ba.25 (3 were purchased)
  • 3-Bred Ba.25Idro for the Naval Aviation (only 1 was purchased)
  • 21 Caproni AP-1 (7 were purchased)
  • 5 Caproni AP-1Idro-for-Naval Aviation (none were purchased)
  • 3 Caproni Ghibli (2 were purchased)
 
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