Upvote:0
This is also essentially speculative, but it is worth remembering that innovation is driven by perceived utility. If, as seems to be the case, raw copper deposits could be exploited without smelting there was little impulse to start processing copper ore with heat. The recognition that copper is too soft to be a useful alternative to stone fore tools when there was an abundance of suitable stone may also have muted the impulse to experiment that would have led to smelting. Only with smelting would the alloys have been discovered or the process to exploit iron.
Since negative questions are much harder to answer than positive question, it may be more useful to consider what were the social and cultural conditions that led to smelting in other parts of the world, in particular the broader social and cultural pre-conditions that led to copper smelting in Western Asia. There may also be a resource factor too, where the state of them the unrefined copper ore may have mitigated for the use of heat early on to separate the copper from other elements mixed in with the copper.
Upvote:3
Because they never discovered the technique of iron making.
As you know, to make iron requires only the ore, clay, hides for the bellows and charcoal. All of these items are commonly found everywhere. Even very primitive African tribes used to make iron using these simple materials. It takes about a week of work by three or four men to make enough iron for an axe head using the most primitive methods. Of course, such an axe would be worth a fortune in pre-Columbian America.
Technology is an amazing thing. Once you know how to do something new, entire worlds open up.
Upvote:5
(A good part of this answer is speculation.)
There were areas of the current U.S. with moderately stable, non-nomadic farming communities before Columbus. However, there were few, if any, large cities, the tribal governments were not very well organized, and the labor and economic systems were very weak and disorganized compared to Europe, Asia, and Africa.
This made it much more difficult to develop organized projects or industries that required a lot of labor, which resulted in less overall demand for iron and made it less likely for an iron industry to emerge. The small tribal governments also made large wars unlikely, which eliminated another source of demand for iron.
It seems likely that iron from meteorites or surface deposits was used in a limited way, but the knowledge probably didn't spread and most artifacts have likely long since rusted way.