wolf_brother
Banned
The thing is that there was no ironworking tradition at all in the Americas prior to the arrival of the Europeans. Gold and copper saw extensive craftsmanship in the Americas, but iron never took off. I think it was because the metal working cultures didn't live near iron deposits or something like that. Iron does require a bit of fiddling around with to get right, but it doesn't get too tricky unless you're trying to create steel.
The Tarascans, the traditional imperial rival to the Triple Alliance (aka, Aztecs) were beginning to use iron weapons by the time of Cortes. However after seeing their foe destroyed by so few men they submitted to the Spanish in 1522 instead of fighting a war they believed they would have lost. If the Tarascans had fought on the Spanish would likely have been pushed out of the region; the Tarascan army, conservatively, numbered at least 100,000 and they had a strong series of border forts and an advanced logistics system.
Also, the Inka worked with iron extensively. However they didn't value it for the same purposes that the Tarascan or Eurasians did. Heather Lechtman (1) states that Europeans sought to optimize iron and other metals "hardness, strength, toughness and sharpness" for tools and weapons. The Inka, by contrast, valued "plasticity, malleability, and toughness." Andean societies used it as a token of wealth, power, and community affiliation. While large-scale Eurasian-style molten alloys from molds were known to the Inka, she found they preferred to hammer metal into thin sheets, form the sheets around molds, and solder the results; one bust analyzed was less than an inch tall by made of twenty-two separate gold and iron plates joined together.
Both the Inka and other states along the Andes, and the Tarascans, lived near large, easily accessible iron deposits. As well the Fort Ancient cultural complex also lived near surface iron deposits; however unlike the other two the upper Mississippians did not have the prior experience of working with copper, bronze, etc, to pave the way for iron working.
(1) An archaeologist at the MIT Center for Materials Research in Archaeology and Ethnology, quoted in Charles C. Mann's 1491.