Mexico and Central America have plenty of ancient, monumental structures (e.g., Chichen Itza). But the continental US and Canada do not. Why?
In: Engineering
The biggest group of Indians in North America were the Mississippians. They were dominant all the way from the Midwest to the Appalachian mountain chain as well as the southern states. They did build similar monumental structures as you find in Central and South America. However they built them out of dirt instead of stone. They are therefore far more common then further south and even bigger. But they tend to blend into the landscape a lot more when overgrown. And a lot of them have sadly been destroyed as people settled on them or used the dirt in the mounds for construction materials.
If you look into the Indian cultures in Long Island, New York, Quebec, etc. there is a lot more stonework. But this is some of the most disturbed archeological sites in North America. We even have written accounts of colonizers having to siege Indian cities and eventually defeating them in battle and using the existing city walls for their own forts. These were sadly mostly destroyed in upgrades and eventually the materials reused for buildings as the city grew.
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