Native Americans were the first slaves and filled many niche economic roles in North American colonies for decades. Disease decimated populations over the long term and by the mid18th century access to African labor for use in an export staple economy completely dualized by race edged them out of the labor market completely, although many of their ancestors still remained in the labor force until emancipation as evidenced by a large number of successful freedom suits brought by their descendants.
Indian slavery was not only ubiquitous (New England, Virginia, the Carolinas) but it also played a huge role in the development of legally codified slave laws, the development of domestic labor markets, Indian-Anglo political relations and conflicts, and development of the concept of race in general that since was used to oppress those of African heritage for hundreds of years. And that's just in British North America, much less the Slave regimes of Spanish Central and South America.
Native Amerixan slavery both existed and was important. If you want I can recommend evidenced academic works published in peer-reviewed Ivy League university presses I f you have further questions.
