When did the concept of "a free country" arise, and what did it mean? It seems to have been in use in the 1600s. Here it is in a tract written, apparently, around 1689 in England:
https://archive.org/details/bim_early-english-books-tract-su...
The freedoms in that instance are freedom of religion, and democracy. (Democracy, the franchise, was limited to about 10% of men, under rules that varied locally from "you have to own a house" to "you have to own the entire region".)
But here the concept is again in ancient times:
https://archive.org/details/BiblicalCollectionPrintedBetween...
This is (a translation of) Josephus, writing in the first century about a speech by a Roman senator from the time when Claudius was put on the throne, with lines like "our natural freedom", "breath of liberty", and "the Liberty of former Times, that was dead and gone before ever I came into the World ..." I can't work out what that freedom was all about - Claudius came after Caligula, though, so you can make a good guess - but evidently this kind of concept is much older than the United States.
I also found the phrase "it's a free country" in Uncle Tom's Cabin, where the freedom in question is the freedom to control slaves.
So the concept is:
• Not modern,
• Not well defined,
• But not meaningless, either.
My meaning is more like, St. Nicholas and his flying sleigh and reindeer have existed since at least the 1800s, Father Christmas as well, Sinterklaas even earlier most likely, but Coca-Cola invented Santa Claus as the world knows him in 1930s, and the USA did the same for the modern concept of "free country" or "democracy." A couple decades of radio, television, and film dominance was the method.
Running with that metaphor, Sinterklaas (freedom and democracy) actually exists, and even when people invoke the Coca-Cola version they're still aspiring to something with a grain of truth to it. It doesn't merely simplify to "us and them" but also contains some actual meaning relating to actual forms of freedom, when people take the trouble to add the depth back in instead of lazily designating outsiders.