The implosion of Argentina is a very complex issue, but, essentially, the country allowed itself to be informally dollarized and ceded control over most of its industries to international (read corporativist) interests. When Perón restructured the country, it was done with a limited scope and with relatively short term changes, causing their economy to collapse again later (it doesn't help that Brazil, a powerful potential ally, had undergone a rightwing U.S.-backed coup at the time). Then, the whole Falklands/Malvinas war happened, all rightwing bullshit, and the country still hasn't bounced back.