Of course it is. Has been since day one.
Acording to wiki it’s a little more complicated than that:
The Constitution requires the government to support Roman Catholicism economically.[15] Despite this, the Supreme Court ruled that the Roman Catholic Church was not granted the status of official religion by the constitution or any federal legislation.[17]
The Constitution once stated that the president must be a Roman Catholic. This requirement was removed from the text in the 1994 constitutional reform, since the president no longer designates Argentine bishops. The old 1853 text also included a goal “to keep a pacific relationship with the Indians and promote their conversion to Catholicism”, which was deleted in the reform.
The federal state pays a salary to Roman Catholic bishops. Each bishop receives a monthly salary that is set by law to the equivalent of 80% of that a judge, about 4,300 pesos or 1,430 USD.[15] Older seminarists and retired priests receive minor pensions, and parishes in conflictive and border areas are subsidized with 335 pesos per month (112 USD). As of December 2005, and after recent conflicts with the national government, the Argentine Episcopacy is considering the possibility of forgoing this support, in favor of full independence.
http://en.wikipedia.org/wiki/Religion_in_Argentina