The balance of power looks like it was mostly determined by disease epidemics wiping out Native American population concentrations at the 50-90% rate, Charles Mann's "1491" has a lot of interesting stuff on that and William McNeil's books on the impacts of plagues on history are amazing in how they change one's opinions about the importance of weapons technology or imagined industrial base. Balancing that is probably ongoing contact with Eurasia so frequent smaller plagues and acquired resistance, a genetic resistance to a wide range of diseases would be up into Alien Space Bats POD.
Iron and steel technology would probably be best coming over from China to "Fu Sang" and materials science always matters in many, many ways. Unfortunately the iron ore and coal deposits are on the Atlantic sides of the continents mostly so Viking tech transfer (or Phoenician/Minoan, Roman, etc.) would be key, maybe just better diffusion as Arlington Mallory found Viking-tech iron foundries at several Northeast locations in the 1930's-1940's in his book "Lost America" (photos included and metallurgical analysis included.)
Domestic livestock could be solved two ways, either llamas and alpacas are brought by sea to Central and North America where they spread. Or Viking horses are brought over in greater numbers and have spread further although there was an interesting article tracing them to more of the wild mustang horse population than the Spanish Barb ponies generally credited...partly because the Spanish early enough were bringing geldings in their expeditions rather than mares and stallions (just as few knights, cavalry, or cowboys ride other than geldings) which apparently most historicans didn't notice geldings don't breed prolifically.) The mildest wonk is probably not to have horses and camels die out in North America for unknown reasons between 8-12,000 years ago (you'd also retain mastodons/mammoths for India-style muscle-power in dragging logs and building stone/ore which'd be a big advantage.) The plains and woodland bison in North America are superior to cattle in just about everything but convenience in fencing or milking, actually a competitive advantage to Europe. Chinese contact would bring over pigs and chickens as well as teaching duck domestication, but food production other than in droughts is something the Americas are better at already in this era than Europe (better developed crops and higher yield/lower input/terrain adapted farming methods.)
I recall reading the Incas did turn out to have some bronze (lots of copper in their regions-Chile, Argentina, etc. while tin is in Bolivia, not sure where zinc is there) but didn't turn it into the mass production, many uses that Euraasia did, which either contact with heavy bronze users or the minor POD of "hey, let's try this!" would resolve that. Bronze would expand their coastal shipping that was seen on both continents' coasts by the early explorers and that explains lot like getting people onto the islands in the Carribbean and sustaining those populations. More trade, faster ideas spread and the river systems in both continents eclipse Europes while there were big civilizations along them (Adena-Hopewell, Mississippian, Amazonian Basin, etc.).
Without the big die off of Indians, their numbers would trump the quite small quantity of horses, attack dogs, arquebusses and wheelock guns (they already had swords, body armor, tactics, trained veteran warriors, etc., the edge of the Spanish is mostly measles, smallpox, chickenpox, whooping cough, mumps, etc.). With bronzeworking more spread, capturing some bronze cannons from Cortez or Columbus etc. shipboard cannons on the ships that wrecked or were dismantled, casting new ones would be a learning curve but not a big one...gunpowder artillery at this point is far more important than small arms, and matchlock muskets are very low tech. The Native Americans are less "primitive cultures" and more cultures with very different scientific development and political organizations from 16th Century Europe, it's just taken a lot of research to realize and admit that (as conquering primitive savages is the classic rationalization of killing inconvenient populations.)