You remember Cortez? I didn't say that South American Indians ain't Indians, I said that the conquistadors who got off the boat from Spain 500 years ago to rape and pillage south America are not Indians nor are their descendants as indigenous as they claim they are after ONLY 500 years.
If your beef is "Rob claimed" well then that's just because whatever he said off camera as a private citizen is not canon, because whatever "Rob claims" the writer/producers could have made an episode that contradicted his claims at any point in the series run.
If Rob wanted to do more than "claim" then he should have written an episode about Chakotay like Bob did about the Doctor. It's not impossible to be heard when you're that close to the heart of the matter.
I checked with Google on Tropical plants and the Rubber tree. Outside of a greenhouse the website I breezed through claimed that they weren't native to or happy if some idiot tries to plant them in North America.