Travis's question got me to thinking that may be the relative infrequency of use of ironworking in the Old World was due to the fact that there was no easy availability of bog iron - which was one of the main sources of iron ore in middle ages.
However, upon looking, it seems that there were areas in modern USA territory that were very rich in bog iron.
Is there any research/writings explaining why bog iron smelting didn't get invented or at least widely used by the tribes in North America? Intuits/Escimos did use the meteorite iron, so it's not like there was no precedent; and I'm pretty sure that at least some tribes were at the development levels significantly exceeding that of Hittites (who were presumably the original inventors of iron working technology in the Old World).
Was it coal availability?
Easy availability of replacement materials making iron not needed?
Lack of settlement where bog iron areas were?