Before World War 2, the German Bund played a big role in American politics, generating sympathy for German-Americans, and even for the Kaiser and the Hitler regime, at least until Pearl Harbor.
But in the end, in both world wars, Americans of German ancestry played very pro-American roles, a fact that cannot be forgotten. General Ike Eisenhower was only one among many.
Nevertheless, it was true for some time that the Bund attracted Americans who identified with the Kaiser in WWI and with Hitler in WWII. I also know of a German-American who went to France before the U.S. entered WWI to drive an ambulance at the front, a very dangerous assignment, and received the Croix de Guerre from France. Many German-Americans were passionately pro-American.