All those sites talk about a hemispheric supernation (your words). You said most free traders wouldn't support hempispheric supernations, yet you can clearly see from the links that a plan to integrate the hemisphere has been active since 1994 using trade agreements.
Integrating trade under fair rules is not the creation of a hemipheric superstate. It's a voluntary and reversible agreement to cooperate for the benefit of all in trade matters.