Did the Red Indians follow a heavenly religion or were they pagans? What is the meaning of the Quranic verse in which Allaah the Almighty Said (what means): {And never would We punish until We sent a messenger.} [Quran 17:15]?

All perfect praise be to Allaah, The Lord of the Worlds.  I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

We do not know the religion of the Red Indians before the discovery of America in modern times. Regardless, whether they were following a heavenly religion that reached them at the hands of a prophet of Allaah The Almighty or not, there is no contradiction in the meaning of the mentioned verse. 

The meaning of this verse is that Allaah The Almighty will not punish any of His creation until He has informed them beyond any excuse of ignorance, through Prophets and their messages.

Therefore, if the message of the Prophets did not reach these people in the past or the present, then Allaah The Almighty will not punish them, according to the explicit meaning of the mentioned verse and other similar verses. 

Thus, they are treated like those whom the message of the Prophets did not reach, and Hadeeths (narrations) signify that they will be tested on the Day of Judgment. 

Allaah Knows best.