How did the U.S. Constitution view Native American tribes?

The Constitution does briefly mention the Indians and Indian tribes.

Article I, Section 2. (later superceded by the 14th amendment) states that non-taxed Indians would not be counted as part of the population of the states used to determine Congressional representation.

Article I, Sec. 8 grants Congress the power to regulate trade "with the Indian Tribes."

These sections seem to imply that Native American tribes were seen as politically independent entities.

as any other nation. Like England, France and Spain.

as I sit and think about your question, it comes to me that the constitution does not address any particular group.

nothing in constitution concerning that.

As non-citizens

They, like the blacks, were NOT viewed as "We, the people..." NOT LOL...

It didn't.