In the West, the main groups of people were Native american tribes. European explorers unwittingly brought along plague and small pox which killed off most natives over several decades. European explorers also brought along their techniques of farming, hunting, fighting, city building and many other things. These techniques marginalized the natives and promoted European dominance in the New World. The demographic of the new world changed from natives living off the land (in a minimally invasive way) to European settlers pushing westward and settling on native land by cutting down trees and exploiting the land. The majority of the east coast was forest before the Europeans came. Now, when you drive on the highway on the east coast, there is major deforestation and the large trees are all mostly gone. The new world changed from a heavily forested unspoiled land to a deforested mini Europe.
Meanwhile in Europe, plants, fruits and vegetables like corn, tomatoes and coco beans were all brought back to European countries. These plants revolutionized food and culture in the "old world." Tomatoes were suddenly included in dishes that before did not exist. The Italians for example, employed the use of tomatoes in their pasta and pizza dishes. Far in contrast from the now crowded cities of Europe, the New world was seen as a vast expanse of land where one could restart their life. In the early colonization of the new world, the majority of settlers were wealthy nobles. The columbian exchange became the catalyst for an ever expanding middle class of merchants. The new world also allowed European manufacturers a new place to offload their produce and new materials to make things with. Tobacco is a great example of a new product that had no place in Europe