Two ecozones would be different it they had two different climates
The cascade volcanoes were formed by the subduction of the Juan De Fuca, Explorer and the Gorda Plate (remnants of the much larger Farallon Plate) under the North American Plate alone the Cascadia subduction zone
Greenland is an autonomous country with the Kingdom of Denmark. although Greenland is geographically a part of North America continent, it has been politically and culturally associated with Europe for about a millennium