Depending upon which tenets one considers to be essential to fascism, one can argue that the dominant political philosophy of 19th century America was democratic fascism. Manifest destiny was highly nationalistic. presumed that American culture was superior to both that of the aboriginal inhabitants and that of our neighbors Canada and Mexico. In the words of the fourth stanza of The Star-Spangled Banner, "Then conquer we must, when our cause it is just, and this be our motto" 'In God Is Our Trust.' "
fascism wouldn't contain this qualification.
Fascism thinks their cause is just. It's why for example Hitler didn't want to fight Britain. He didn't view it as a just war since England too was an Aryan nation in his view. While it would be horrible to contemplate, I think Hitler would have been quite willing to not only negotiate a peace with Britain after the Fall of France, but also to honor it. Whether his successors would have is a different matter.