Tolerated? Some welcomed it and some actively fought several wars against it and lost. Many tribes conducted some kind of economic transaction that traded land for something else.
Various California native people practiced slavery and indentured servitude on each other before the arrival of Spanish Catholics. The Mayan people went further than that.
Still do. Slavery is perfectly legal in modern day USA, it's enshrined in the constitution
> Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
Which is functionally the same as
> slavery or involuntary servitude, as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
Actually the two are very much not the same logically. The real text quoted first allows for servitude in limited circumstances. Your second modified version requires it.
