Answer:
One direct effect of westward expansion and environmental transformations that occurred after the Mexican-American War was the displacement of Native American populations from their lands and the destruction of their way of life. As settlers moved westward, they encroached on Native American lands, leading to conflicts and wars. The environmental transformations that accompanied westward expansion, such as deforestation and the overgrazing of grasslands, also destroyed the habitats of many Native American tribes and disrupted their traditional ways of life. Additionally, westward expansion and environmental transformations led to the depletion of natural resources, such as water and timber, and the extinction of some species.