A large number of Americans generally seem to grow up with a main character complex thanks to all the individualist & jingoist propaganda people get bombarded with over there.
The search for something “exotic” as you put it is just an ego-driven search for the piece of evidence that they are, in fact, more special and unique than everyone else.
If you’re an American and you’re not a native American you’re family immigrated here. Why is it so weird to want to know where your family or ancestors come from, I’m lucky and can trace my family name back a couple hundred years. I’m still American I just got family history that’s fun to know about.