¿Can Mercosur consolidate itself as a predecessor to a “South American union” in the style of the European Union?

As we know, the European Union was formed through a process involving pre-existing institutions, governmental ideas, and geopolitical tensions prior to the bloc's formation. So my question is: can or is Mercosur destined to be one of the institutions that, in the future, will allow for the formation of a "South American Union"? What challenges does it face?