Although copper working was known in North America, it was only in South America and Mesoamerica that copper smelting from ores took place. In the most of North America the source of copper was metallic nodules and nuggets rather than from ores. Iron tends not to be available in this form. (edited)

One significant impediment to the production of iron was due to the techniques used to produce pottery. The general consensus is that old world metal smelting grew out of observation of the byproducts when trying alternative pigments and glazes on pottery. In pre-contact America, pottery was fired using the open pit method which does not produce temperatures as high as kiln based methods.

To get to iron you need even hotter temperatures from burning charcoal, coal, or coke.

You can see similarities in the shape of a blast furnace compared to a bottle kiln for pottery.