Argentina is heavily Italian, more so than it is Spanish actually, as evidenced by Pope Francis though Argentinian born is of Italian ancestry only and no Spanish blood. And we all know Argentina was also pro-Axis. Paraguay was also pro-Axis, and has had German immigration of significant influence notable in that a German descendant- Alfredo Stroessner, became president soon after WWII. There's a reason South America was a popular destination for Nazis fleeing from war crime tribunals, plots were plenty to turn Paraguay in particular into a Fourth Reich. Peru has a significant Japanese immigrant population to boot. Argentina and Japan had their first embassies established in 1940... that's in the middle of the war! Ties weren't severed until 1944. With all the wars and border conflicts throughout South America it is not unlikely or ASB to see one or more decide that it would be a good time for revanchism. Paraguay, Peru, Ecuador, and Bolivia all had scores to settle. Being "scared of the US" is more an ASB a reason to NOT join the Axis than it is a realistic reason as to why the South American nations did not in OTL. As Argentina in the 1980s can tell you- they aren't scared of wars that might piss off the US.
President Roca brought German advisors to modernize the Argentine Army by the start of the 20th Century, which cause a Pro-German tendency among the army.
The economy, however, was geared towards exporting food to Britain, to the point that, during the early 1930s and the protectionist policies brought worldwide because of the crisis, the Argentine Foreign Affairs minister defended a trade treaty with the UK by saying "Economically speaking, for all intends and purposes, Argentina is a part of the British Empire"...
as a good thing.
In 1939, after the sinking of the Graf Spee in the River Plate, the Argentine government consulted with the UK and the USA about passing a resolution which, while short of a declaration of war against Germany, would declare Argentina as a pro-Allied neutral. The American government told the Argentine government not to do it and then caused a diplomatic incident the next year by leaking that.
That's your "Pro-Axis" government.
But you will tell me "Hey, but Peron was an antisemite who received two (yes, two) Nazi war criminals who entered the country with fake IDs!"
First, not only Peron came into power in 1946, but Argentina also received some 8,000 jews after WWII (on top of the hundreds of thousands who had immigrated in the decades before). That's 4,000 surviving jews per Nazi criminal. Peron also had warm relationships with the State of Israel and the local Jewish community. You can read more here
http://www.clarin.com/sociedad/Raanan-Rein-Peron-catapulto-argentina_0_1418858444.html
And, BTW, I miss the part in which Japan was at war with the Allied powers during 1940