https://upload.wikimedia.org/wikipedia/commons/a/a7/Census-2...

Large numbers of people report their ancestry simply as "American."

I would actually argue this is the origin of a lot of political divisiveness in the US. It also sort of boils down to the "America as an immigrant/proposition nation" vs "America as a settler nation" debate. The former seems to be ascendant in the past few decades but it's definitely not consensus.