The funny thing is I bet ending birthright citizenship is an amendment that could actually be passed. You don't have to be a virulent racist to think the context has changed when you can get almost anywhere in the world in about 24 hours.

(I'm not sure where I stand on it but I can at least see an argument for revisiting the question)

I'm guessing that you did not actually read his dissent.

Far from agreeing with the Trump administration; his view would effectively end birth tourism but preserve birthright citizenship (and maybe even stronger) for the children of non-citizens, legal or otherwise, who are domiciled in the US.

As for it being cut and dry, do you earnestly believe that "and subject to its jurisdiction" is cut and dry? You might have your view, you might have some historical receipts for it, others have other views, and historical receipts, and others rely on common law readings. There's no single unambiguous interpretation of this phrase. Thomas's dissent is well reasoned and has ample historical antecedents and if adopted would have been the best possible interpretation.

It was one vote away from going Thomas's way, so I wouldn't say it doesn't matter what he thinks.

As a non-american, I would have enjoyed the precedent that the logical conclusion had to be that I would not be subject to the laws of the US, when visiting.

The Thomas interpretation must logically have given diplomatic immunity to anyone on an ESTA too.

It's also amusing that you won't ever hear conservatives like Thomas making the same argument when it comes to, say, the 2nd amendment.

Right, because they might find themselves agreeing with it! Can't have that, democracy thrives in darkness with a closed and restricted 'marketplace of ideas'.