Venezuela has been, for years now, a favorite sobering tale for the Brazilian Right to point out as the "failure of the Left". The part about the collapse is very much real, to the point that the refugees here in Brazil have become a significant worry.
Maduro has a very anti-American discourse, and I am certain that he is clinging to it at this time of disaster more than ever, since it is one of the very few reasons he can offer for people to keep tolerating him. The "USA is evil" discourse is very popular in South America, albeit not very uniformly and certainly not very mature at all.
I do not expect that Maduro hopes to survive (politically and perhaps otherwise) if any significant USA help is accepted by Venezuela. The idea alone would anihilate his credibility, such as it is. Difficult as it may be, he certainly prefers to try and weather the situation by itself or with the help of foreign governments that are perceived as having proper "anti-imperialist" credentials.