Of course they were concentration camps. American citizens were unlawfully hunted down, forcefully removed from their property, detained without due process, stripped of their possessions including homes and family businesses, and 'concentrated' into 'camps', supposedly so they couldn't render wartime assistance to the Japanese Empire. They were beyond "guilty until proven innocent", as none of them were ever given the opportunity to prove their loyalty to the United States.
A concentration camp is a concentration camp. It's immaterial if one is a little nicer than another, or if the food is of a higher quality. The essential point is the function they serve, and on this point, U.S. concentration camps served the same purpose as Nazi Germany concentration camps - cruel detainment of innocent men, women, and children.
That's Roosevelt for you. A concentration camp-loving fascist.