Here's one reason why birthright citizenship is important in the USA.
Suppose my citizenship is questioned. Mine specifically, I mean. The government wants to deport me, detain me without trial, take away my voting rights, or prosecute me for being in the country illegally.
I have an easy answer to this. I produce my birth certificate, which says that I was born in New York State in 1969. They confirm this with the New York State Department of Health, and that is the end of the matter.
Without birthright citizenzship, with the regime that Alito and Gorsuch want, it's *not* the end of the matter. The government can look at my birth certificate, scoff, and demand that I prove my parents were here legally. And they can imprison me until then.
Okay, but I can prove that they were here legally. After all, they were citizens from birth. I produce my parents’ birth certificates, showing that they were born in New York State in 1939 and 1943 respectively. Do you see where this is going?
But that's not good enough because without birthright citizenship, just being born in the USA is not good enough. I also have to prove that my grandparents weren't here illegally.
And proving that my grandparents were U.S. citizens is not good enough. In fact my paternal grandfather was brought here as a child, 1913. Can I prove he was here legally? Perhaps his immigration paperwork contains a misstatement of fact, his naturalization was void all along, my father has been here illegally for 87 years, and I am subject to immediate deportation to Hungary or El Salvador or South Sudan.
Without birthright citizenship, every person's status is in precarious.