[Sherman Logan]

The treatise that spells out legalities as far as citizenship under a constitutional republic was by all accounts quite popular with those same Founders.

And which treatise might that be? Certainly couldn't be Law of Nations, since there was no constitutional republic on the planet when Vattel died.

The US created the very first written constitution and therefore the first constitutional republic.

Vattel was writing for a European audience. The British government of the time, for all its flaws, was more free than any European government with the arguable exception of some of the Swiss cantons and the Netherlands. Or perhaps Poland, if you were an aristocrat. Of course, the Polish aristocrats were at the time in the process of destroying their nation with that freedom.

[RegulatorCountry]

Vattel advocated a constitution, the legislature and the independent judiciary in Law Of Nations, Sherman. He laid out the groundwork for a constitutional republic, and the United States is a constitutional republic. The lack of such in Europe at that time, particularly in the three hundred or so states of "Germany" is a topic upon which Vattel spcifically commented. You really should attempt to understand the work you're dismissing.

[El Gato]

The US created the very first written constitution and therefore the first constitutional republic

We had a written constitution, before the Constitution was written. But there are plenty of written constitutions which greatly predate the US, or even the settlement of the Americas.

For example, the Swiss Federal Charter of 1291 which was admittedly only of 3 cantons, but it grew, eventually becoming modern Switzerland.