A great read about Nativism, immigration, and more by venerable labor historian, Eric Foner. Here is a clip:
Adopted as part of the effort to purge the nation of the legacy of slavery, birthright citizenship remains an eloquent statement about the nature of our society and a powerful force for immigrant assimilation. In a world where most countries limit access to citizenship via ethnicity, culture or religion, it sets our nation apart.
Or at least, we used to recognize citizenship as stemming from more than ethnicity. Today, not so much.