Mhm, yes, but I guess (very unsubstantiated personal opinion) it is not a question of some "power" that exists as some objective entity waiting to be talked to... As I understand, it is more an ability of certain people to connect to "something" we usually describe with slippery meaning word "intuition". Those "powers" described are culture specific and you are right - if someone wants to imitate them or experience exactly that, it is impossible and even meaningless - especially if you are not from that culture.
But it is interesting to hear the opinion of a very esteemed scholar on this subject that also translates and explains some phenomena in a more universal langauge.
He doesn't give recepies - "do that to achieve that"... But you could get more concrete after reading this book, you may even want to try to fast and spend some days alone in the nature of your land and concentrate on certain eternal questions and expect nothing. Why not? You can know that those cultures used this deep concentration, fasting and isolation for connecting to this "something". The basic method or concept is universal - if you don't expect to immitate the more culture specific aspects of their ways (like concrete songs, prayers, dresses, ritual behaviour) and visions - this concept of undertaking can be applyed by anyone interested.
In the "worst" scenario you loose some weight and breathe some fresh air and concquer the fear of being alone in the nature (esp. at night)... If you expect to gain some super-powers or become an "Indian shaman" then you are lost even before you start, I guess.
Equivalent persons in "western culture", although I wouldn't exclude Vine Deloria Jr. from that cultural sphere either - he was priviliged to walk on both sides - would be people like David Bohm, Francis Crick, the long list of different philosophers that were/are concerned with the question of consciousness and other "metaphysical problems", etc.
But I think you're wrong that persons outside the native cultures don't have access to this undefined and unresearched yet territory. There are many anecdotal accounts that "proove" otherwise.
I even personally know a certain ("white") woman from the Balkan region, where many "superstitions" still live, that can find lost objects with her intuition and has quite strong intuitive insight into near future events or possible health problems when concentrated on a person or a specific problem.
She prooves it all the time (and I know what "cold reading" is..), but I still have a very ambigous opinion on her. Everything shows that she really has some "gift", but I still have this doubt that she maybe "guesses well" or is just very good at cold reading the persons... I respect her, since she is a very good and honest person and I know her personally, but nothing "reasonable" can be said about that ability of hers.
You can only report it and leave it open for different and oposing interpretations. But even if it is open it shows that also non-native cultures have this access to "something".
(that "reporting thing" is actually what Deloria did - report the cases he thought were valid to some extent and gave some practical and philosophical opinions and advices to "his people" at least)
Until it is more accurately pinned down I am not willing to give it names and attach too personally to any given hypothetical answer - stemming either from Western philosophy or Zen Buddhism or Native American ways, but studying various ideas gives you at least a little better blurry picture what might it all be about.
I have a hard time believing many of less-philosophical and more concrete "mystical" accounts, but I am also willing to acknowledge that the Universe has probably the laws that work outside our linear causal explanation of the world.
But also an opinion that there are some "powers" that some nations can obtain and others don't is a very hypothetical one and not very helpful in a pursuit of truth - it can even hinder you to explore those regions of the mind if you think you have no mental or "spiritual" access to anything besides the causal, materialistic description of the Universe.
It is arrogant for us to believe that we know enough to pass the final and firm judgements what is real and what is not. This book is good to read also because of such realization...