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.
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.)