“He trashed his American citizenship for French.”
He probably has both at this time.
My understanding is that, per basic International Law, a country cannot make a person “stateless” meaning a non-citizen of any country in the world. So, for us normal people with single-country citizenship, our government cannot revoke our citizenship.
But if we did have dual citizenship, then, well, George, you might need a visa to visit the US, and with that visa your ENTIRE history, particularly in social media, might get a full-up *^&@ exam...and if we don’t like it, you could try slipping-in from Mexico (but you’ll get caught now).
The US needs to de-naturalize him.