An old story

Nineteenth-century "U.S. expansion into the Southwest was built on a Comanche antecedent.  Comanches are at the center of the story and the westward-pushing Americans remain in the sidelines, stepping in, often unknowingly, to seize territories that had already been subjugated and weakened by Comanches.  The narrative does not ignore the vast imperial ambitions and resources of the United States, but it shows that the stunning success of American imperialism in the Southwest can be understood only if placed in the context of the indigenous imperialism that preceded it."

     Pekka Hämäläinen, The Comanche empire (New Haven and London:  Yale University Press, 2008), 142.  This on top of the impact that the Comanches had already made upon Anglo-Americans and other immigrants, the French, Mexicans, and especially the New Spanish (i.e. the Spanish Empire) throughout much of the previous century.