The EO only calls for elimination of birthright citizenship on a prospective basis. It would not affect anyone who is currently a citizen. It would simply be marked on your birth certificate if you were a citizen, based on whether your parents are citizens (either one). This is not at all remarkable, and plenty of countries operate this way. The US is somewhat anomalous in granting citizenship to children born to tourists or illegal immigrants, simply because they were in the US when the child was born.

wait so if you give birth as a tourist in the US your kid has to fill out IRS and FBAR forms each year even though they only lived in the US for their first week or whatever?

Yes, unless they renounce. They might also not be able to invest in their home country and things like the sale of their home are taxed by the US. Starting a business or buying an etf are also fraught with peril.

The only other remotely similar country is Eritrea

Not if they never plan to actually live there, I imagine.

You'd still have to apply for a Social Security Card for them to have anything to worry about. That's not automatically granted to babies at birth. The hospital should certify the birth and give you paperwork from something like a state's vital records department but you still have to present that to the SSA. Ostensibly yes they are automatically citizens of the US but they're in a weird spot I would think that you could resolve with a court case if the IRS suddenly came after them for back taxes or something when they were adults. Honestly that sounds like such a ridiculous situation that I can't imagine it's happened.

> It would simply be marked on your birth certificate if you were a citizen, based on whether your parents are citizens (either one).

hmm, perhaps with a gold star, or a pink triangle?

Probably it would just say, like it does in so many other countries. No need for crypto-conspiracy theories since it's a totally normal thing in most of the world.