Australia is the better team on paper, & they translated that paper strength onto the field. I don't see where the "mental block" comes into it.
If NZ was the better team on paper & couldn't win a series at home, then you've got a case for a mental block, but otherwise it's just getting beaten. It's the severity of the beating that's embarrassing combined with the fact that most of the squad have near no experience in NZ conditions, certainly no Test experience (all except Smith, Khawaja, Hazlewood, Lyon & Marsh).
Now, does that mean the Test was unwinnable? Not by any means, but too many things needed to go right, & it's frustrating that it is like that, but it is what it is.