From The Penguin History Of Latin America, by Edwin Williamson (Penguin, 2003), Kindle p. 332:
The Second World War turned out to be a watershed for Latin American industrialization. The worsening international situation had exacerbated the historic rivalry between the armed forces of Brazil and Argentina. Sensing the drift to war in Europe, the military establishments in both countries wanted to develop their own armaments industries instead of relying on imports. But the manufacture of arms required the setting-up of steel and electrical industries, and so from the 1940s the armed forces of Brazil and Argentina pressed their governments to develop an industrial base. Furthermore, as the outbreak of war created strong international demand for raw materials and foodstuffs, the Latin American export-economies boomed, and as wartime conditions abroad reduced the flow of imports, especially luxury goods, Latin American countries were able to build up large surpluses in their balance of payments: this enabled national debts to be paid off and led to the accumulation of domestic capital for investment in industrial projects.
The USA played a decisive part in fostering industrial development during these years. Needing Latin American raw materials for its war effort, it offered loans, technical expertise and equipment to assist the Latin American countries in their programmes of industrialization. During the early 1940s numerous US missions went to Latin America and signed trade agreements. The major republics duly declared war on the Axis powers and supplied the Allies with minerals and commodities. The notable exception was Argentina, where sympathy for Italy and Germany within the military junta caused it to adopt an awkward neutrality, for which it forfeited the kind of technical and financial assistance from the USA that Getúlio Vargas was getting for Brazil. The lack of US aid was an important cause of the economic difficulties which General Perón had to face in the post-war years and which contributed to his downfall in 1955. Still, even though the USA helped Latin American countries to initiate industrial development, the policy of industrialization as such was the late product of the nationalism that had evolved since the turn of the century, intensifying in the 1920s and 1930s.