Japanese internment was propelled by a long history of racism against Japanese Americans on the west coast. Japanese Americans were a small part of the population but they made up a disproportionate part of the farming and fishing economies and there was a lot of jealousy from white farmers who resented the competition. Internment was a way to eliminate the competition and seize Japanese Americans productive farms. Long story short, longstanding racism and jealousy was the main reason for Japanese Americans to be singled out

Racism. German and Italian Americans are white - part of the country's racial (and cultural) majority, so to suppress racial tension, keep the Asian minority from siding with 'the enemy'.

American soldiers fighting in the Pacific also often made racist acts, there's a wikipedia page about it here. American mutilation of Japanese war dead