During the War, the United States Government actually did put German and Italian Americans into internment camps. President Roosevelt put out Presidential Proclamations 2525 (Japanese), 2526 (Germans), 2527 (Italians) immediately after the attack on Pearl Harbor declaring:

"all natives, citizens, denizens, or subjects of the hostile nation or government, being of the age of fourteen years and upward, who shall be within the United States and not actually naturalized, shall be liable to be apprehended, restrained, secured, and removed as alien enemies"

Just like many Japanese-Americans, German and Italian Americans also stayed quarantined, were limited to which wartime roles they could work on the homefront. Indeed some German and Italians did hold Pro-Axis sympathies as I previously wrote here