Neither of the above instances you site are actually parallel Earths.Good summary. Then there was one monoculture (miramanee) and two cultural contaminations (nazis and gangsters) but a narrative to connect the others would be nice.
In "Patterns of Force" a federation observer who was also a historian decided to interfere with the culture he was observing (because they were anarchists and militant and killing themselves); and he formed a government based on Nazi Germany as dispassionately he viewed that country as the most efficient one Earth ever knew. His plan might have succeeded except for an Ecosian who wanted power for himself and drugged the observer (John Gill) and effectively took over.
In "A Piece of The Action" that society was contaminated by a history book on gang warfare in the 1920s (which was left behind by a starship before the non-interference directive went into effect); and that planet's inhabitants used / took the book as a template for how to establish a working form of government.
In "The Paradise Syndrome", The American Indian society that existed there was actually transplanted from Earth itself onto that planet by a species who referred to themselves as The Preservers. They roamed the galaxy and if they saw a society in danger of extinction, they would transplant it to a world they considered safe where the society could continue to thrive. As these American Indians were in a environment that supported their way of life; they felt no need to advance technologically in any way, and pretty much remained as they were from the time they were taken (which is assumed to be the 19th century of Earth).
So yeah the other episodes you describe, while they were imitations of aspects of Earth's society; they were not true parallel Earths in and of themselves.