It should be noted that while in general metallurgy was less advanced in America, there also was a domain where it was more advanced than in the rest of the world.
There is one metal that has been discovered by the South-American natives, before the contact with Europe, and which was unknown elsewhere: platinum. The Europeans have learned from them about platinum.
Moreover, not only the South-Americans had discovered platinum, but they had also developed a technology to make objects of platinum. This is no small achievement, because platinum was impossible to melt or forge with the means available at that time.
The South-Americans had worked around this, by inventing a form of powder metallurgy. To make things of platinum, they sintered platinum powder and nuggets with gold.
This technology has been lost after the Spanish occupation, so the Europeans have developed techniques for platinum processing only much later, around the end of the 18th century and the beginning of the 19th century.
While platinum itself had been unknown in the rest of the world before the contact with South America, some platinum-group metals had been known, i.e. the natural alloy of osmium with iridium was known in the ancient Egypt, Greece and Roman Empire, in the form of nuggets that were mixed with those of gold in alluvial deposits. However none of the ancient Mediterranean people discovered any method for forging or melting the Os-Ir nuggets, so they were called "adamant", i.e. "untamed" (which has been distorted in the modern "diamond"). This was the original meaning of adamant/diamond. Only after the wars of Alexander the Great in India, the Europeans have learned about what are now called "diamonds", which were then named by the Greeks and Romans "Indian diamonds", to distinguish them from the Os-Ir diamonds. Later, the knowledge about Os-Ir nuggets has been forgotten and the references to them in Hesiod, Platon or Pliny the Elder have been mistranslated until now.
The Mayan discovering platinum and maybe working it a bit had no perceptible effect on their civilization, if only because a few bits of it did not provide an opportunity to use it.
Iron and steel, on the other hand, are transformative to civilization and the Romans made extensive use of it. For example, nails make it easy to build wooden structures.
(Gold and silver are also rather useless for pre-industrial civilizations, as they are not strong enough. Their usage was confined to decoration and currency.)
Platinum was worked mainly in the territory of present Colombia and Ecuador.
Some jewelry may have been traded until North America, but they would have been certainly rare by the Mayan.
Because the South-Americans did not have iron or iron alloys, but they had rather abundant gold and silver and platinum, the usage of precious metals was not confined to decoration and currency. For instance the use of nails made of gold-copper-silver alloy was frequent and also various tools were made from such a gold-copper-silver alloy (named "tumbaga" by the Spaniards).
Pure gold, silver or copper are extremely soft, but their alloys can have a decent strength, even if not comparable to steel.
The discovery of platinum in South America had a significant impact on the entire human civilization.
Initially the Spaniards have despised the metal because, unlike for the gold and silver that they took back to Europe, nobody would give anything in exchange for the unknown platinum, and they also did not know how to work the metal into useful things. Hence the Spanish name of the metal, "platina", as a diminutive of "plata", i.e. silver, as at that time it was much less valuable than silver.
Nevertheless, platinum samples have been taken back to Europe, and eventually, in the middle of the 18th century they have arisen the curiosity of the chemists, who began to study its properties.
After it was established that platinum is an ideal material for vessels used in chemical research, due to its resistance to chemical reagents and high temperatures, platinum has played an exceedingly important role in chemistry around the end of the 18th century and during the 19th century, i.e. during the time when the majority of the chemical elements have been discovered, frequently during analyses performed in platinum vessels.
Other early important use of platinum was for the standards of mass and of length of the metric system, which ensured an accuracy and reproducibility of the measurements much better than anything before that.
I have mentioned these things precisely because they are very little known by the general public and even by those who are supposed to be professionals in such domains. Because of this, references are scarce.
References about the platinum technology in South America before the arrival of the Europeans:
"Ancient Platinum Technology in South America, its use by the indians in pre-hispanic times", by David A. Scott and Warwick Bray, Institute of Archaeology, University of London, 1980.
"Metallurgy of Gold and Platinum among the Pre-Columbian Indians", Nature, 1936.
About the knowledge of the natural osmium-iridium alloy in the ancient Mediterranean world, there are several archaeology articles with chemical analyses of Egyptian gold artifacts, most of which contain as inclusions small nuggets of osmium-iridium alloy, whose cause is the fact that the gold was collected from river deposits, where the gold nuggets and the Os-Ir nuggets accumulate together, so when the gold was melted it incorporated the Os-Ir nuggets. (For instance: "The analysis of platinum-group element inclusions in gold antiquities", N.D. Meeksa, M.S. Titea, a British Museum Research Laboratory, London WC1B 3DG, England)
These archaeological finds match perfectly the description of adamant from Plato (in "Timaeus" and in "The Statesman"), where adamant is described as the "knot of gold", which is found together with gold, but it cannot be shaped like gold, because it is too hard and impossible to melt. The same description of adamant is provided by Pliny the Elder in his tenth book, which adds besides it the description of the Indian adamants, which are completely different from the classical adamant, being octahedral crystals, not metal nuggets, which matches what are now called diamonds.
The earliest reference to "adamant" is at Hesiod, who describes how Gaia has made a sickle blade from "grey adamant", for the castration of Uranus, which makes no sense as a reference to modern diamonds, which are neither grey nor suitable to be forged into a blade, but it makes perfect sense as a reference to the grey Os-Ir alloy, the hardest metal known to Hesiod, which humans were too weak to forge, but surely a huge goddess like Gaia should be able to forge. Other references to Os-Ir adamant are in Aeschylus (Prometheus is bound with chains made of adamant; another use that makes perfect sense for a metal, but which would be impossible for fragile diamond crystals, which cannot be forged into chain links) and in Theophrastus.
There are a few other articles about the history of platinum and platinum-group metals that have relevant information about all these things, but I do not remember now the titles or authors.
The fact that by searching the Internet you can find a lot of incomplete or even completely incorrect information about many things proves that one should never trust the answers given by an LLM for any really important question, because an LLM will provide the information most likely to be found in its training sources, while truth cannot be based on democracy. On the contrary, much too frequently the majority opinion is more likely to be incorrect, than the minority opinion.
