The environment on the Great Plains did affect the way of life of the Native Americans. However, we must realize that they did not simply get acted upon by the environment. These were people who were themselves trying to shape their environment in ways that would be helpful to them.
The environment had many impacts on the Native Americans’ ways of life. For example, you can argue that the environment affected their religious and spiritual beliefs. Some scholars like to argue that sheer scale of the landscape of the Great Plains, and the powerful weather that occurs there, made the Native Americans more likely to understand and even to worship the power of the natural world. Another example is more economic. We can say that the environment of the Great Plains caused the Indians to become largely dependent on bison for their livelihoods. This led them to learn sophisticated ways to hunt the huge animals.
But we must realize that the Native Americans affected their environment as well. They did things like creating agricultural economies in river bottom land. When horses came, some Native American groups tried to alter the environment to help raise more horses which were the basis of their economy.
In these ways, the Native Americans were affected by the environment but also had an impact of their own on that environment.