I've read several bios of Eisenhower and I never heard him referred to as a "German-American."
He wasn't - it was his name that was the problem. His political opponents used it to smear him; in fact, there were dark mutterings during the early days of WWII that someone named Eisenhower couldn't be trusted to fight the Germans and hence certainly shouldn't be in command of the ETO. (These were the same sort of folks who referred to the president as "Rosenfeld" for similarly spurious reasons at the same time). During the presidential elections of 1952 the same crapola came up - they were doing the "politics of personal destruction" back then as well. It was a non-issue, but it sure ticked Ike off.