What is the tectonic structure at the base of the North American mainland?

The foundation and basis of the continent of North America is the ancient North American platform, which was formed during the Paleozoic and Mesozoic eras.
This platform covers 75% of the mainland, and only on a third of it can be observed a sedimentary layer with folded structures, such as: the Cordillera Mountains, which find their continuation in the mountain ranges of Northeast Asia, as well as the Appalachian Mountains. The Canadian Crystal Shield should be highlighted as the protruding surface.