Please review the plausibility of all that follows. What I will be doing is organizing the contents of Bronze Age New World into a formal year-by-year timeline.
--
~450-500: An isolated group of Arawak Indians in northern Venezuela develop more advanced navigation technology than in OTL. This entails a long-range trade-and-exploration ship with the following description: double-hulled canoes, similar to Polynesian vessels, with a large square sail, a sharp bowsprit, bowlines, and a bowsail. The hulls are burn-shape-scrape dugouts, rigging is made out of woven grass. Large steering oars are used on one side. For short range travel, monster canoes paddled by oarsmen are used, a cross between Northwest Indian canoes and an Anglo-Saxon oar-ship.
This isn't as good as what the Polynesians developed, but its better than OTL and good enough to cross large stretches of blue water.
~500-1300: The *Arawaks take to the seas in force. They raid Mesoamerica periodically for centuries, Viking-style, devastating coastal polities and civilizations, picking up treasure, foodstuffs, slaves, but most importantly technology such as agriculture, architecture, and writing. Their warriors don't penetrate any area more than a two-day's march, though... this means that a damaged Mesoamerican civilization is able to manage in the highlands of southern Mexico.
~700-1300: The *Arawak civilization reigns as the supreme power of New World side of the Atlantic. They are aggressive and expansionist, setting up colonies on every stretch of coastline they can find, from South Carolina to Brazil. Their power is established through very advanced Neolithic technology, they never quite shift into a pure agricultural civilization, instead they are gardener-fishers with major farming areas few and far between. The reason for this is because their culture gives farmers a very low place in their society... no tender of the earth can be treated with any respect, in contrast to noble seafaring warriors. Simplified Mesoamerican hieroglyphs are transformed into a Phoenician-style alphabet, which allows for extensive record-keeping, and thus social stratification and specialization.
~950: The chaos of the *Arawak raids has been encouraging some serious tinkering with weapon technology. In this year, some unsung genius mixes copper and tin together to make a blade. In OTL the Mesoamericans knew of bronze... they just needed to be able to recognize its use as a metal for tools and weapons. Bronzeworking spreads through Mesoamerica, slowly but steadily.
~1000-1200: Though the *Arawaks never quite reach the Azores, as they don't like heading too far away from 30 degrees North, and they never reach Europe, they do make it to the Old World. At some point the *Arawaks make contact with the Guanches of the Canary Islands, off the coast of Morocco, but its so far away that only a few round trips are made... a number more voyages stay at the Canaries and never return, fearing for their lives. As such, the Guanches become a divergent peoples from OTL, they have a copper tint to their skin, and they navigate between their islands in catamarans with big square sails. There are a few *Arawak loan words and a few artifacts, but nothing that will affect history later on too much.
~1040: Near the site of OTL Baton Rouge, a slave revolt breaks out in the northernmost *Arawak city. The slaves are of mixed ancestry, but the revolt is led by those imported from Mesoamerica. When the revolt succeeds, they attribute its success to their gods. They cut their former masters' hearts out one by one.
~1050-1250: Freed from the *Arawaks, a new civilization arises in the Mississippi valley, a unique combination of *Arawak, Mesoamerican and Mound Builder cultures. The society is not very pleasant: they are warlike, xenophobic slave-owners, socially stratified, fanatically religious. They practice human sacrifice, ritual torture, and cannibalism. Outsiders are considered slaves at best, snacks otherwise. They raid the Plains Indians so intensively that the neighboring region, some 100,000 square miles in area, is almost completely depopulated. The Mississippians have tobacco and use it in all forms: cigars, pipes, chew, snuff. They also have developed a strong corn beer which is used in various unpleasant religious ceremonies. They have simple bronze horns for music... no bells or gongs. Government is through a number of regional god-kings, all owing titular allegiance to the Undying King in *Memphis. Its titular because the Undying King is strangled and buried every year to keep the corn growing.
~1100-1150: The *Arawaks finally pick up bronze-working after repeated exposude to bronze weapons from their Mesoamerican enemies and vassals. Through the *Arawak colonies the technology quickly takes root throughout the civilized portions of the New World.
1148: A group of *Arawaks on a large canoe, headed to the Canary Islands, incidentally makes landfall on the Moroccan coast, near Agadir. Within a week, half of the group is slaughtered by Almohad slavers, the other half taken in chains. The enslaved *Arawaks soon perish from disease or overwork. Their huge canoe, with a great face painted on its sail, is seen as a piece of idolatry and an offense to Allah, and as such the Almohads burn it on the beach it is found. A few gold ornaments and pots make it to the market at Rabat, but otherwise nothing remains of this transatlantic contact.
~1150-1180: An *Arawak trader discovers the Amazon, which the native inhabitants call the River Sea. *Arawak sailors treat it as a curiousity, sailing down to its mouth to catch a few freshwater fish and fill their canteens. In a couple of decades, the natural port of *Belem is discovered and regular trade begins... no actual settlement at first, just a destination of choice for the annual trade fleets and the occasional slave raid.
--
At their height, the *Arawaks are sailors, warriors, and aristocrats, sometimes traders, artists and musicians, never farmers. Their cities look towards the seas. Their musicians play flutes carved from human bone and capped with bronze or gold. Women wear skirts of carmine and ornaments of jade and coral and gold. Architecturally, their houses are great round towers of slave-quarried stone. They sleep in hammocks, enjoy long barbecues, and communicate long-distance by blowing conch-horns in set patterns. They love pets: parrots, dogs, margays, sloths, parakeets, ocelots, jaguars, iguanas, monkeys. Men are judged by battle scars and tattoos identifying different ranks and proficiencies. It is a proud and warlike culture as much as it is rich and complex.
--
~1200: The *Arawaks reach Bermuda, where they find several thousand acres of Bermuda cedar. A small colony of loggers is planted... the cedar is useless for shipbuilding, but is used to make expensive, sweet-smelling furniture which is shipped southwards.
~1200-1205: Slavers sailing up the River Sea land near OTL's Prainha, where they recognize tin in the black sand along the banks of the river. Word gets out about it, and within a few years instant boomtowns spring up between *Prainha and *Belem, the latter acting as a more convenient port on the way to the Caribbean. None of these are successful, the tin is too low-quality and not economically feasible in any way, but there are other products discovered. Parrots and monkeys for pets, for example. There is also an odd-looking red berry with black seeds that the natives trade to the *Arawaks for bronze axeheads [this is guarana, a plant that possesses the highest content of caffeine found in the natural world]. The seeds provided a pleasant stimulating effect, especially when roasted, ground into a powder and mixed with water. By 1250 no *Arawak anywhere in the Caribbean could concentrate on his navigation without his morning cup of "river berry". These products sailed north while trade goods and immigrants sailed south.
~1220-1230: Crop yields drop alarmingly among the colonies of the River Sea, this due to the poor quality of the soil next to the Amazon. This problem is solved purely by accident: a river berry magnate blames his slaves for not increasing food output, and exchanged them with a Mississippian slave ship for Mayan slaves. The Mayans are some of the best jungle farmers in the world, and are quickly able to end the food shortage when their techniques are replicated. This actually creates a food surplus, allowing for more leisure time to find and manufacture trade goods.
~1250-1350: A Mesoamerican culture copies *Arawak ship design but on the Pacific coast. The boats are small, inferior copies of the Caribbean craft, but they're good enough for coastal trade. Sailors trade obsidian, gold, beads, bronze, jade, and quetzal feathers, every year traveling a bit further north and south.
~1270-1350: The *Arawak civilization, widespread but never stable, begins to collapse. The great cities on Cuba and Hispaniola have teetered on the edge of Malthusian catastrophe for generations. Due to the neglect of agriculture, the soil has been exhausted and there is a growing reliance on slaving to top off the malnourished labor supply. *Arawak cities are extremely specialized in particular manufactures or foodstuffs, very reliant on trade. The *Arawaks need large trees for their war canoes, but they have never developed the idea of conservation, and deforestation becomes a problem. Constant warfare has thinned out the master class, which leaves the cities more and more vulnerable to slave revolt.
War in famine are joined around the year 1300 by another horseman. The tloggotl virus, which has spent several centuries adapting to life in human hosts after jumping from the guayazi marmoset, a popular pet throughout the Caribbean. Widespread malnourishment renders whole populations vulnerable, and the turbulent movements of invaders and refugees give the microbe new fields in which to grow and spread. Tloggotl is a cousin of OTL's Machupo virus, a distant relative of Ebola. A hemorrhagic fever, it afflicts its victims with swellings that fill with pus. Severe cases resemble elephantiasis, which adds a demoralizing effect. This is a virgin-field epidemic, and casualties run over 20%, with many survivors scarred and sterilized.
Plague, famine and war feed off each other. The final collapse is rapid. By the 1330s the *Arawak civilization has been gutted. A few colonies survive here and there, on the *Arawak's frontiers, but the main culture has ceased to exist. Populations on Jamaica and Santo Domingo drop by 90%, while some of the smaller Antilles are altogether emptied of humanity.
~1300-1350: The Bermudans have by this point lost the art of navigation. Contact with the mainstream *Arawak civilization was tenuous from the beginning, and with the latest catastrophes, and the deforestation of the island, the Bermudans have become completely isolated.
~1300-1350: Amazonian natives upriver of the *Arawaks adopt the Mayan agricultural techniques in stride, being close to organized agriculture already. Soon every settlement from *Belem to *Manacapuru is following some version of the ancient Mayan agricultural calendar. Every four years the forest is cut down in August and the remains are set on fire the following March, creating an intermittent ribbon of fire a thousand miles long stretching along boht banks of the river.
~1320: A trade ship from *Port of Spain docks in the *Belem harbour. It carries most importantly a letter from the king of *Trinidad to his Amazonian counterpart telling him the news from the Caribbean. The king of *Belem ignores the reports of plagues, famines, slave revolts and various bloody strife, thinking them exaggeration. The trade ship then leaves *Belem with some goods and never returns. No *Arawak ships from the Caribbean return. For the next two centuries the River Sea becomes completely isolated.
~1350-1400: Traders from the Pacific coast of Mesoamerica have reached the head of the Gulf of California and the mouth of the Colorado. There's also regular trade down to Panama and the Pacific coast of Colombia, where rumors are heard of a strange, rich civilization still further south.
~1390-1450: An outbreak of pneumonic Rocky Mountain Spotted Fever hits the Arkansas Mississippians, the vector being a Ute Indian from Colorado which was enslaved and brought far east to be ritually cannibalized. RMSF will spread over the years throughout the civilization, from Texas to Lake Erie. It kills 5% of its victims and blinds or cripples another 10%.
~1400: Colonization and stimulus-diffusion from the Mississippians has spread agriculture, writing and bronzeworking north along the Mississippi and its tributaries. There are small fortified towns as far north as OTL St. Paul.
~1400-1500: The Mississippians, as violent and cruel as their civilization is, begin developing new engineering and architectural techniques to help them tame the irregular floods of the Mississippi River. This includes complex levee systems, clay plumbing, the cofferdam, and the float valve. At the site of OTL Memphis step pyramids and a temple complex that rivals those found in Egypt. Near OTL Little Rock they mark the boundary of their civilization with a 120-foot stone obelisk, carved with the deeds of the God-King of *Arkansas and bathed in the blood of a thousand slaves. They almost invent the arch, but not quite.
~1400: In OTL's Maryland, there are a dozen towns of more than 2,500 people. This is the heartland of the *Chesapeake city-state culture, stretching from Norfolk to Baltimore. Its the youngest civilization in the New World, but its as technologically advanced as any other society, and quite wealthy. Their diet consists of corn, beans, pumpkins, domesticated turkeys, and numerous varieties of fish and shellfish from the Chesapeake and the numerous nearby rivers. They aren't very warlike, compared to the Mississippians or Mesoamericans, but there is constant bickering between the city-states, also ritual warfare that could be called Flower War-Lite, more like violent sport that leads to few, but very expected deaths. No human sacrifice, nor god-kings... the *Chesapeake city-states are very liberal for this hemisphere. The city-chiefs are limited in power, checked by tradition and councils of tribal elders. Their architecture is not as impressive as the Mississippians, but they are the continent's best metal workers and brilliant potters. The *Chesapeake produce gorgeous artwork, clever tools, and scribing is a respectable position. They are not enthusiastic navigators, but they occasionally sail as far south as the Okefenokee to trade with the *Timuchans and as far north as Cape Cod for whaling with bronze-headed spears.
~1400-1500: In Mesoamerica, the Tlon Empire is dominant. They are somewhat similar to OTL's Aztecs: they are aggressively expansionist and they have a huge extravagant capital city in Lake Mexico. But they're too different to be labeled *Aztecs. They use bronze freely, have the *Arawak navigation package, some notion of the wheel (not very useful without draft animals, but its allowed them to create a messay, two-man version of the potter's wheel), and they aren't nearly as unpleasant: human sacrifice forms only a very occasional part of the their religion, and always voluntary. There are more of them, too. By the 1390s, traders have made contact with the Incas, bringing back the potato and sweet potato by 1430. Tlon agriculture rapidly becomes more productive, and with bronze blades they can clear more land. By 1500 *Tenochtitlan is about half again as big as in OTL, and there are several other cities in the 20,000+ range. Contact with the Incas also gives the Tlon the guinea pig by the year 1400 and llamas by 1460. Llamas thrive in the highlands of central Mexico. They won't be used to bear riders, but they'll carry heavy packs of food and weapons, allowing Tlon armies to march further and faster. By the 1490s the Tlon Empire is about twice as large as OTL's Aztec state, covering all but the northern third of modern Mexico and much of Guatemala.
Tloggotl is a problem, with epidemics hitting every generation or so, with particularily nasty ones striking ~1450 and ~1490. But well-nourished populations are somewhat less vulnerable, and every generation is more resistant than the last.
~1450: The Incas develop bronzeworking, thanks to trade with the Tlon to the north. Curiously, they reject other innovations, such as writing, finding them ugly compared to the knotted-cord quipu.
~1450-1500: The Mississippians grow decadent. There are frequent slave revolts, as well incursions from bronze-armed barbarians from the northern lakes. They have arrived at a solution to pneumonic RMSF, though. The Mississippians regard the spots of the disease as a 'Kiss of the Earth Spirit'. All those who bear them are promoted to demigod status, which involves having one's brains knocked out and then being cooked in an oven for a day and a half. It isn't pretty, but it works in containing the disease.
~1500: The *Chesapeake are consumed with a new cultural development: the song-shaman. He endlessly walks between the cities, carrying a hickory staff, a fan of kingfisher feathers, wearing a kilt and a medicine bag of bison hide. He sings and tells stories to all, and they are respectfully provided food and shelter wherever they frequent.
~1500: The Timuchan in northern Florida are very similar to their OTL counterparts, but have a significant *Arawak cultural and genetic influence, thanks to colonies that were planted in the area. They have bronze-working, boats that sail to the mouth of the Mississippi and to the city-states of the Chesapeake, avocados and corn beer. They are a very tall people, with men standing more than five and a half feet tall, as such, their warriors are reknown as stoic giants. The Timuchan are heavily tattooed, and most adults are expected to be tattooed from head-to-toe, women included. Even as tattooing is so popular, clothes from animal skins and cotton are popular still, and alligator boots, belts and globes are highly-prized. To make room for more tattoos to be seen, the Timuchan cut their hair as short as they can, some using sap to strip it out by the roots. Politically, the Timuchan are divided into several chiefdoms, all unified into one confederacy. There is a lot of bickering between chiefs and the elders in the head council, but war-making is relegated to outsiders only. The culture is not very expansionist or aggressive, but fiercely protective. Boys identified as warrior stock are recruited from all chiefdoms to the Ribbon City, near OTL Miami, the ceremonial capital of the Timuchan Confederacy, where they are trained and assigned to different borderlands in order to guard against raiders. Those who fail to perform admirably are sent back home by the council of elders, where they nevertheless provide a centralizing influence to their various chiefdoms as former denizens of the Ribbon City. Those who are worthy soldiers eventually take multiple wives at the Ribbon City, each sent from various parts of the Confederacy, where they create noble warrior lineages that compete and intermarry with one another. This has the effect of creating a melting pot in the City of Ribbons, where people do not identify as being part of a chiefdoms but as part of the Timuchan people. There is one gruesome thing the Timuchan do: all warriors slain in battle have their right leg, left arm, and scalp dismembered and shipped to the Ribbon City, where on the roof of some stone tower each body-part is tied to the top of a long wooden pole. Three poles to each slain warrior. That warrior's living family is expected to provide ribbons of alligator skin, which are tied to these poles. When all that is left is the bone, these remains are tied up in the alligator skin and carried in a pilgrimage to Lake Okeechobee, and deposited as close to the center of the lake as possible. It is a key religious tradition amongst the Timuchan and gives the city its name. Each building is expected to have three poles on its rooftop, with alligator ribbons flying and human limbs stinking. When the Ribbon City does not live up to its name, the warrior-nobility pushes for ever more grim suicidal expeditions northwards. Religion is very polytheistic and mystical, not given too much importance, but bears interesting similarities to Tantra.
[Doug Muir said very little of the Timuchan. I decided to fill the gap with some of my own ideas on what they might look like.]
~1500: Bermuda has grown very strange. Women fish, farm and hunt for seabirds. Men maintain wells and cisterns of fresh water, take care of the remaining groves of Bermuda cedar, and construct elaborate towers of stone, mud, and wood, some reaching more than a hundred feet. These spirit towers are a work of art. Each artist-builder, at his death, will be flayed, his tattooed skin adorning the tower, his skull sitting atop his spirit tower looking out to sea. Old towers are allowed to decay, scavenging materials from them is sacrilegious ut commonplace, a frequent source of clan feuds. Its bizarre.
~1500: The jungle is reclaiming the great cities of Hispaniola and Cuba. The islands are inhabited only by the descendants of the *Arawaks' slaves. They are few, shy, and primitive. Their bronze tools have long ago corroded, and no one can remember what a ship looks like. Slash-and-burn fields of corn and cassava provide for the natives deep in the forested interior of the islands... the cyclopean ruins that dot the coasts are for them places of dread and horror, where the Shapeless Death may still lurk.