Argentina needed industrialization. All western Powers, and Japan and now CHina, arose from massive protectionism and subsidizing of heavy industry in its nascent stages.
Listen, I am a free market guy. I don't like countries acting like India and subsidizing decrepit, inefficient iron smelters and such. Plus, tariffs create trade wars, which kill economies. I realize it is counter-intuitive.
But, to quote one of my favorite rock bands
The Scorpions, "No pain no gain."
The problem with Argentina is that they had it too easy. They had a cattle economy and so, trade barriers and protectionism would have
really hurt as they were resource-export based.
Just think of a victorious confederacy...they would be like Argentina today if they continued with slavery, open trade borders, and a pure-agro based economy. King Cotton is a pauper when compared to Mr. Industry.
So, Argentina needs protectionism. It's going to such initially. They can boost their agriculture by giving away free land to European and domestic homesteaders. They will have to subsidize heavy industry and pretty much give up on their military. They will have to squander tons of money on ambitious industrialization projects, like SOuth Korea in the 60s and 70s.
Then, perhaps after WW1 after they get rich exporting to desperate western allies (who are in no position to care about tariffs), they need to start rescinding these things, as the US did in the 20s. Then, come 1930 when the US starts a huge trade war with their tariff, if Argentina avoids protectionism and gets off the gold standard quick, and goes full blown Keynesian in investing in domestic infrastructure (particularly rails, port facilities, an roadways) Argentina may be in a good position to export manufactured goods in WW2, even if they have to import tons of iron from the US.
After WW2, Aregentina can outbid devastated Japanese companies in bringing in manufacturing experts
W. Edwards Deming,
Homer Sarasohn and
Charles Protzman. Plus, they can have very friendly immigration policies for Europeans looking to leave Europe after WW2. With a flood of cheap labor, and a shot in the arm with the masterminds of lean manufacturing, Argentina could actually be a modest industrial power (it lacks the population of Japan, so I still think Japan would be the true rising star of the post ww2 period.)
Today, Argentina would not be like Japan (which thrived of dirt-cheap labor), but it could be a modest industrial power more wealthy per-capita than modern Italy ( which it was at the turn of the 20th century, and Italy OTL was devastated after two big wars.)
Of course, you would need a lot of lucky elections without dummies running the country to make this happen. Probably, something that gets their military completely out of the picture (not sure how, perhaps a quick lost war against the US, such as an Alliance with SPain during the SPanish American war) could do it.