It is federal, because it is the government of States united in a political union, in contradistinction to a government of individuals, that is, by what is usually called, a social compact. To express it more concisely, it is federal and not national because it is the government of a community of States, and not the government of a single State or Nation.
Alligator: The crocodile of America, superior in every detail to the crocodile of the effete monarchies of the Old World.