Well, you obviously know the history. You can see as well as I that cultures with regular psychedelic use tend to be incapable of defending themselves from even very casual incursions by foreign powers.
And cultures without regular psychedelic use tend to initiate casual incursions into foreign lands; practice enslavement, genocide, overpopulation and overuse of resources and industrial pollution; and maintain strict hierarchies that benefit the few at the expense of the many.
If such a dominator culture, indeed now the dominant culture, were to stop repressing the use of psychedelics, there seems to be little danger of it being taken over--it's already all but quashed the competition. It would with any luck help to curb the excesses that are the cause of so much trouble, and help to provide the will to use the fantastic tools we have made to better ends.
I can't for the life of me understand what your point is supposed to be. You're making an observation that the particular civilization that led a campaign of violent global colonization was one that had a hostile attitude towards psychedelics. Yes, that is a correct observation. What kind of generalization are you trying to make from that though?
I'm pretty sure that a nomadic lifestyle, massive technological disadvantage and vulnerability to pathogens played a bigger role in that than psychedelics, but feel free to prove me wrong if you have a credible source on what you are implying.
This isn't limited to the Americas.