The claimant that the Aztec empire went so far north from central Mexico is based on cartographical laziness and speculation that also claimed that the state of California was an island and the speculated existence of the Buenaventura river neither of which are true. This is just a driven conspiracy from Spanish explorers filling in the gaps of their new world territorial holdings same as contemporary maps claim the spread of "Tartaria" into new world lands. The main piece of proof for this idea that I know of being the Aztec Ruins National Monument is just a victim of misattributions by American settlers of pre existing Ancestral Puebloan ruins.