It’s amazing. I was at a pretty large wedding several years ago, and after dinner the DJ ran a trivia contest. One question was “Who was the first Republican president.” I was the only one of the guests who knew the answer.
A better question would be to ask people who Lincoln was. I’ll bet you a sizable percentage of Americans, mostly Dems, wouldn’t know who he was. My brother knew an adult employee who didn’t know who Lincoln was. The man was born and raised in the U.S.