Why didn’t official reports that were critical of u. s. government policy toward native americans have a greater effect on the american public?

Well, it because it mostly will  not effect their living.
People tend to respond to incentive. So if a cause is pretty much will not affect their personal living in anyway, most people will usually give little thought about it or ignore it completely. 
This is why those reports did not have a greater effect

Ais your answer