The “confidentiality” is a matter of a simple majority.
Took Congress 4 days to go from Pearl Harbor to using Census data to round up citizens for incarceration based on race.
“Stroke of a pen, law of the land. Pretty cool.”
My research shows that, although Pearl Harbor was bombed in 1941, the request for census data on Japanese Americans was not made until 1943 because of a personal threat vs. President Roosevelt. However, by that time, Japanese Americans had already been relocated to internment camps, per executive order in February 1942.
So, request for census data was not used for internment purposes. The request pertained only to Japanese and Japanese Americans living in the Washington D.C. area. Again, I am not an expert on this but this is what research reveals.