"I thought S.Americans could be more assertive. We've seen this cockpit gradient problem in the Far East & SE Asia, but S.America?"
You obviously haven't paid any attention to, for example, Geert Hofstede's work on Power Distance. South American countries have some of the highest ratings on this scale, just as high as many Asian countries. A high Power Distance rating basically means it's extremely difficult for subordinates to challenge the person in charge in any given situation.
https://geert-hofstede.com/national-culture.html