Pelle, You give a good analysis! Here's an additional distinction between Argentina and the U.S. which (I believe) is also a factor...
In the 19th Century, both nations had vast tracts of land relatively undeveloped...
The U.S. essentially "gave" the land away to vast numbers of its citizens if they'd work it... encouraging and then creating a great class of free-spirited, industrious entrepreneurs with their own capital!
Argentina transferred its land in vast tracts to wealthy landowners and created essentially a division between the wealthy elites and the landless peasant!
The secret to capitalism FAILS when wealth becomes too concentrated... (remedying this is a focus of mine).