The Mayans developed incredible pyramids

Pyramids were popular architectural forms throughout the Americas (and elsewhere obviously). While my personal favorite example is Mesoamerican, it's not Mayan. But you're asking for differences between Mesoamerica and the rest of North America. Here's the first: they were probably building pyramids long before the Mesoamericans were (at least as far as we currently know).

For almost a thousand years, starting about in the mid-17th Century BCE, the Poverty Point Culture flourished in the lower Mississippi Valley. Their cultural center, Poverty Point itself, is located in what is now northeast Louisiana. The site is composed of a series of massive concentric earthen rings and several flat-topped earthen mounds. Of the mounds at Poverty Point, the Bird Mound is the largest and is among the largest mounds in North America (depending on the estimates, it’s vying for second place with the nearby but much later Emerald Mound; Cahokia’s Monks Mound has a firm grasp on first place).

The Poverty Point Culture were contemporaries of the Olmec in Mesoamerica. While the Poverty Point Culture built the Bird Mound sometime between 1400-1200 BCE, the Olmec’s wouldn’t begin their Great Pyramid of La Venta (also an earthen mound) until sometime around 1000 BCE. The Great Pyramid of La Venta is among the earliest pyramids in Mesoamerica. La Venta’s pyramid weighs in just shy of 100,000m^3 of earth, making it less than half the size of the Bird Mound by volume.

Now you might be saying to yourself that while the Woodlands and Mesoamerica both began with similar earthen pyramids, the Mesoamericans went on to build stone structures too, an architectural medium more appealing to Western sensibilities. In the Woodlands, earth and wood were the preferred building materials, with stone being used sparingly. There are a variety of reasons for this, some practical, some cultural. At Poverty Point, for example, has features that suggest its architects were deliberately evoking prior architectural traditions of the region going all the way back to the earliest earthworks, such as Watson Brake, a nearby site built almost 2000 years earlier. Earthen structures like these were traditional symbols of prestige and cultural importance.

While Western aesthetics prefers stone for its monumental architecture, it’s important to remember that Eastern Woodland earthworks aren’t haphazard heaps. Their architects took care to choose specific colors and types of earth, both for aesthetic reasons of their own and for important structural support. The core of Monks Mound, for example, is made from a clay that would normally expand when wet and contract when dry, a cycle that would have shaken the whole structure apart over time. The Cahokians foresaw this problem and encased the core in a waterproof layer.

a complex language

I assume you mean a complex written language, right? Certainly North America had its own set of rich spoken language, as everywhere in the world does, full of their own unique twists and complications. My favorite example of such a unique feature is Natchez Cannibal Speech, a specific register used for particular characters in a specific genre of Natchez oral literature, which marks the character as a cannibal.

As far as written language is concerned though, there is no confirmed Pre-Columbian writing system in the Eastern Woodland. Which isn’t the same thing as saying that people of the region had no way to record information. Ojibwe wiigwaasabak, birch bark scrolls, were made in the Protohistoric period (between Columbus and official first contact with Europeans), though we’re not sure how far back they really go. The region isn’t very favorable to preservation of such material and the oldest known archaeologically is from the mid-1500s, about a hundred before French contact with the Ojibwe.

Information was recorded on these scrolls with intricate geometric figures. These figures are similar to Mi’kmaq hieroglyphs. There’s debate whether these figures are a true writing system or mnemonic devise. Part of the controversy comes from the fact that Mi’kmaq hieroglyphs were hijacked by French missionaries early on. The missionaries altered and added (perhaps extensively) to it in an effort to convert the Mi’kmaq. Their new writing sytem proved unpopular and was replaced.

Other systems of recording information included wampum belts and strings, calendar sticks, and winter counts. Wampum belts and strings were widely used throughout the northeast, most famously by the Haudenosaunee (the Iroquios). Different patterns of light and dark beads used to make these items would serve as mnemonic devises for different messages. These items were used for treaties, to convey messages to allies (such as a call to arms), as important parts of ceremonies, and to serve as reminders of important points made in speeches.

Calendar Sticks and Winter Counts were time keeping devices and historical records. In either case, they’re marked with symbols to signify important events that have occurred within a particular year. Sometimes the symbols used are very direct. An all too common symbol on Plains winter counts is a person covered in red spots, marking the various smallpox epidemics that struck the region. For others, more symbolic marks might be employed. For example, among the Powhatan, the year the English arrived in Virginia was symbolized by a smoke-breathing swan. The swan represents English ships, while the smoke represents English firearms. Most of the surviving winter counts and calendar sticks from the Plains and further west; in the east they’re mentioned in colonial records but none that I know of have survived to this day. The Battiste Good Winter Count covers the longest amount of time; made from copies of copies of older winter counts (each generation’s calendar keeper made copied down their predecessors work and built upon it), it goes back several centuries, but unfortunately only covers year-by-year specifics starting around 1700.