The first thing most people think of when they hear or read about shapeshifting is that a person transforms him/herself into another being, like the Sphinx, Minotaur, White Buffalo Calf Woman, or other entities as described in any of the numerous myths and legends, some of which go back as far as the Dreamtime.
Shapeshifting is indeed about transformation, but it doesn't necessarily have to be in the physical sense. Most stories about shapeshifting are either symbolic, or reflect an era in human evolution when our bodies were not so dense and our minds and spirits were more aligned with the Creator. Shapeshifting is a matter of controlling and shifting your energies to suit any given moment and being able to draw upon these energies as needed.
American Indians, like other native cultures, performed rituals according to the natural cycles of the seasons. They were capable of 'walking the paths' that link the physical world with the Spiritual. Their shamans or medicine people would wear animal skins and masks and take on complete identity with these animals and their powers, to aid them in fertility rites, healing ceremonies, exorcisms and so forth. Although these rituals may seem primitive, superstitious and even absurd to our rational minds, they are still as powerful today and the Universal Laws that govern them (as above, so below) are just as viable.
Most of us perform acts of shapeshifting every day without realising it. For instance, when we adapt to change, pleasant or otherwise, or adjust our behaviour to relate to a wide variety of people or circumstances, we are shapeshifters, it's that simple. Animals in the wild are expert shapeshifters. They change the colour of their fur to adapt to the seasons, or to camouflage themselves when they hunt or protect themselves from other predators. Animals can perform these 'miracles' by being in harmony with nature.
In our world we can also perform miracles within our minds, at a different level of perception (using our imagination). With practice we can strengthen our imaginative faculties and learn to consciously control and shapeshift it to anything we desire. And when we change the imaginings, we can change the world!