If by the first golden age, you're referring to the Mexican incursions in the Early Classic by Siyah K'ak', then you might be mistaken as it is highly debatable whether the advances are purely thanks to him or coincidental. The only sure thing is that he got the Mayans to advance militarily. Concerning a Maya renaissance, it's possible but you'd have to end the conflicts between the Cocom and Tutul Xiu if you want any stability in the region. Although there were about 18 or 16 independent states, they could unify under a somewhat religious ruler, the Lord of the Katun, chosen among the governors of the most prestigious cities. This guy was the most powerful person in Postclassic Yucatan, although he ruled for only 20 years before another was chosen.
But you are right about them getting better soil techniques, they already learned from their mistakes. The Postclassic Maya made less colossal structures which took lots of stucco to make. They could easily advance even more, and as you said expand their "empire" through trade beyond the Ulua rivers in Honduras. Also, it is highly probable that the civilizations of the American Southeast will advance to the level of Mesoamericans, probably with Mayan contacts as they were the most renowned seafarers in the area. Literacy via the Mayan script would spread after the so-called Renaissance, as it is partially syllabic than the Mexican scripts and therefore more adaptable.
As the major copper users of Mesoamerica were the Maya (they used copper weapons and made much jewelry from copper) and the Tarascans, it is likely that they'd dominate the area, although what happens to the Nahua and Central Americans after the likely fall of the Mexica is debatable. The Mexica however are not likely to keep the Triple Alliance together, or at least not Mexica-dominated. You can't keep a tributary empire together by threats of destruction for too long. Although the Tlaxcalan Alliance is more likely to fall first to the Mexica, who would then likely fall apart from the inside.
Northern America is likely to see the spread of Mississippian influences, and through them Mesoamerican influences. Bronze weapons however might not be as popular as other things as it is harder for semi-nomadic people to use due to the time it takes. Either way, the existence of the Plains people as we know them are completely butterflied away. The Sioux and Cheyenne and others did exist, but they were farming folk, not the horse culture so highly revered by Americans.
As noted by others, Amazonians are also likely to rise to greatness, more so than the Inca. While the Inca rulers die away and the empire splits apart, the Amazonians are gonna keep on living the high life with their advanced agricultural techniques.