Before America became purely a “proposition nation”, it was also an “ethnic nation”. As Malcolm Pollack puts it here:
Once upon a time, an ordinary understanding of nationalism embraced all of this: love for, and loyalty to, not only shared beliefs, but also for one’s people, their common heritage and traditions, and their homeland. But in these withered times, we must pry it all apart and pare away everything, no matter how common and natural and healthy, that violates our new ideological orthodoxy. We have to be content, now, with what our grandparents would surely have seen as a sad and shriveled “patriotism”: all that is left for us to love about our nation is a handful of philosophical postulates….
There should be no doubt that the founding of the United States rests upon a set of propositions that articulate a theory of natural law and natural rights, chief among which is the proposition that no human being is by nature rightfully sovereign over any other. (This, and pretty much only this, is what the Founders meant when they said “created equal”.) So in that sense it is correct to call the United States a “proposition nation”.
The problem is that nowadays it is all too common to stop there: to declare the United States to be a “proposition nation” and nothing more….
The founders knew very well that for a society based on natural liberty and limited government to flourish would require civic virtue, and a sense of civic duty, and that these in turn required commonality: not just the commonality of assent to a set of political abstracta, but also the natural cohesion of a community of people who share history, culture, traditions, and a broad sense of actual kinship.
John Jay wrote about this in Federalist 2 (my emphasis):
It has often given me pleasure to observe that independent America was not composed of detached and distant territories, but that one connected, fertile, widespreading country was the portion of our western sons of liberty. Providence has in a particular manner blessed it with a variety of soils and productions, and watered it with innumerable streams, for the delight and accommodation of its inhabitants. A succession of navigable waters forms a kind of chain round its borders, as if to bind it together; while the most noble rivers in the world, running at convenient distances, present them with highways for the easy communication of friendly aids, and the mutual transportation and exchange of their various commodities.
With equal pleasure I have as often taken notice that Providence has been pleased to give this one connected country to one united people–a people descended from the same ancestors, speaking the same language, professing the same religion, attached to the same principles of government, very similar in their manners and customs, and who, by their joint counsels, arms, and efforts, fighting side by side throughout a long and bloody war, have nobly established general liberty and independence.
This country and this people seem to have been made for each other, and it appears as if it was the design of Providence, that an inheritance so proper and convenient for a band of brethren, united to each other by the strongest ties, should never be split into a number of unsocial, jealous, and alien sovereignties.
… The American Founding could not have happened elsewhere: swap out the colonial population of 1776 with a random assortment of people from everywhere on Earth and it would quickly have failed. The particularities of the “matter” upon which the American propositions were to act were every bit as determining as the “form” — the propositions — themselves.
But the unique circumstances of the Founding could not be preserved against the onslaught of abstract legalisms, which put the “propositions” of the Founding ahead of its substance: the culture of America’s predominantly British Founders. Examine the lists of signatories of America’s Founding Documents in the table below and you will see, in addition to many duplicated names and family names, only a few obviously non-British person among the 123 listed.
Substantive liberty in America — the true liberty of beneficial cooperation based on mutual trust, respect, and forbearance — could not withstand the onslaught of three forces: (1) cultural fragmentation, (2) the concomitant rise of legalistic abstraction (e.g., free-speech absolutism), and (3) the aggressive growth of the central government, which is both the beneficiary and initiator of the first and second forces.