To adapt the OP's original phrase, I think the US can lay legitimate claim to being the first modern republic, except maybe for the Dutch.
Yes, there were nations with a republican form of government before that, but the purpose of that form was fundamentally different.
The pre-modern republics were set up to allow all the aristocracy a turn at being king, while modern republics are set up to allow the non-aristocracy to prevent there being an aristocracy.
For example, the ancient republics of Athens, Rome, and even Carthage were noted by their neighbors as being especially warlike precisely because, to take Rome as an example, everyone only got six months as consul and so they had to make it by launching wars immediately, both because the plunder would form the basis of their personal and family fortunes and because glory from war was the only goal worthy of an aristocrat. Regular kings, by contrast, could take their time.
In the modern world, we don't respect glory in battle or plunder like we used to, and so we use the republican form of government to prevent anyone from amassing too much power on a permanent basis at all. People often think the purpose of voting today is to select the best leader, or at least a good one, but really it's simply to ensure that the current one has to leave since no one can please the majority of an electorate indefinitely.
Yes, there were nations with a republican form of government before that, but the purpose of that form was fundamentally different.
The pre-modern republics were set up to allow all the aristocracy a turn at being king, while modern republics are set up to allow the non-aristocracy to prevent there being an aristocracy.
For example, the ancient republics of Athens, Rome, and even Carthage were noted by their neighbors as being especially warlike precisely because, to take Rome as an example, everyone only got six months as consul and so they had to make it by launching wars immediately, both because the plunder would form the basis of their personal and family fortunes and because glory from war was the only goal worthy of an aristocrat. Regular kings, by contrast, could take their time.
In the modern world, we don't respect glory in battle or plunder like we used to, and so we use the republican form of government to prevent anyone from amassing too much power on a permanent basis at all. People often think the purpose of voting today is to select the best leader, or at least a good one, but really it's simply to ensure that the current one has to leave since no one can please the majority of an electorate indefinitely.