I can't think of any examples of evidence of large-scale, stone monuments from ancient Native American or Canadian cultures. It seems that every other continent has them (i.e. Pyramids in Africa, Stonehenge in Europe, etc.) I know Mexico and South America have them, which is all the more puzzling to me because I am under the impression that they were the last places to which homo sapiens migrated. So why didn't cultures in present-day United States and Canada develop stone working along with the rest of the world?
Off the top of my head I would say the American Southwest have impressive stone built settlements. There's also numerous medicine wheels dotting the landscape in the northern United States and southern Canada.
/U/Mictlantecuhtli is correct in pointing out the Ancestral Pueblo Great Houses, some of the most famous being Chaco Canyon. Monumental rock effigies in the East include the Rock Eagle and Rock Hawk located in Georgia.
The Bighorn Medicine Wheel in Wyoming is 80 feet in diameter and just one of many examples of the many stone medicine wheels.
The Sun Dagger in New Mexico is an example of carefully carved and placed boulders serving as a solar calendar.
Old Stone Fort in Tennessee is about 2,000 years old so earth has covered its stone walls.
Stone chambers in Vermont and other northern states were once believed to be colonial cellars but have turned out to be far older and are precontact Native American structures.
And some precontact Mississippian cultures buried their dead in stone box graves.
Though not monumental, Etowah, Georgia boasts two ancient, painted, marble statues, a man and a woman, each weighing over 100 pounds.
And probably not what you are thinking of, but definitely huge in size, the Blythe Intaglios are just some of the 600+ geoglyphs in the rocky floor of the Colorado River Basin.
By and large? Complete lack of domesticated hauler quadrupeds compounded by lower surplus/barely above subsistence living. I mean, the Mississippian cultures had pretty damn impressive mounds and the like, but, they had the ability to use waterways as a shipping route. The Mohegans and other Eastern Woodlands did build impressively large wooden structures for ritual purposes but often had them taken down after and reused the wood for other purposes.
Too vast an area and too small population and no foods to grow until about 1500 years ago when corn, squash and beans made their way north from the south.
Mesa Verde and Chaco Canyon are 'cities' made of stone but there's no real 'monuments'... aside from medicine wheels and 'petroforms' across the plains. Places like Cahokia though had 'Aztec style' mounds/pyramid shaped things though.