What is the history of the American military?

the military of America was like this [this is only brief]

the Aztecs ruled the area of Mexico and plain Indian tribes ruled north America

the spanish arrived in Mexico/America and put down the Aztecs then the setterlers from Europe landed in America and after a war the tribes of the north American pains died out then the civil war broke out and the confederates and unions warred now in the modern age troops of America are in Iraq and Afghanistan