The three biggest American civilizations that we are taught about in school are the Aztecs, the Incas, and the Mayans. While I know that the Mayans has mostly collapsed by the arrival of Europeans, what was the relationship like between these three empires? Were there diplomatic ties? Trade relations? Or did they really not know that the others existed?
There's always room for discussion, but perhaps the section Pre-Columbian Trade and Contact from our FAQ will answer your inquiry.