There are a host of similar American propositions, and most of them are fully testable. This is why America has a citizenship test. Would it not be “un-American,” for example, to oppose free speech? One has to understand the axiom and vow to uphold it in order to be naturalized not simply because it is the law of the land, but because it is a foundational principle without which the American idea ultimately cannot operate. This and the other core principles are neatly outlined in the national guidebooks, which include the Declaration of Independence, the Constitution, the Federalist Papers, the Gettysburg Address, and so forth. Such works have made the world intimately familiar with the propositions of the American project and have acted as a magnet to immigrants from all over the globe. In contradistinction, ask somebody what Belgium is for and they will be hard-pressed to answer you — there is no such thing as the Belgian “promise” or the Belgian “dream,” and those who spoke of such things would be looked at with reasonable suspicion.
Anyone can learn to become an American because far from race, religion, or family being the sole determining factor of citizenship, America is built upon philosophical truths that are accessible by anyone capable of reason. This is brings in some interesting implications, the first and most important being the reverse of the propositions stated above. Someone born in the geographic location that is within the country called America may not be "American" in the truest sense of the word. Being American may then, as the Founders would say, be self-evident.
In a speech on July 10th, 1858, Abraham Lincoln has a long meditation on the significance of what our fore fathers did in setting our nation upon a set of abstract truths, applicable to all men and all times:
We are now a mighty nation, we are thirty—or about thirty millions of people, and we own and inhabit about one-fifteenth part of the dry land of the whole earth. We run our memory back over the pages of history for about eighty-two years and we discover that we were then a very small people in point of numbers, vastly inferior to what we are now, with a vastly less extent of country,—with vastly less of everything we deem desirable among men,—we look upon the change as exceedingly advantageous to us and to our posterity, and we fix upon something that happened away back, as in some way or other being connected with this rise of prosperity. We find a race of men living in that day whom we claim as our fathers and grandfathers; they were iron men, they fought for the principle that they were contending for; and we understood that by what they then did it has followed that the degree of prosperity that we now enjoy has come to us. We hold this annual celebration to remind ourselves of all the good done in this process of time of how it was done and who did it, and how we are historically connected with it; and we go from these meetings in better humor with ourselves—we feel more attached the one to the other and more firmly bound to the country we inhabit. In every way we are better men in the age, and race, and country in which we live for these celebrations. But after we have done all this we have not yet reached the whole. There is something else connected with it. We have besides these men—descended by blood from our ancestors—among us perhaps half our people who are not descendants at all of these men, they are men who have come from Europe—German, Irish, French and Scandinavian—men that have come from Europe themselves, or whose ancestors have come hither and settled here, finding themselves our equals in all things. If they look back through this history to trace their connection with those days by blood, they find they have none, they cannot carry themselves back into that glorious epoch and make themselves feel that they are part of us, but when they look through that old Declaration of Independence they find that those old men say that "We hold these truths to be self-evident, that all men are created equal," and then they feel that that moral sentiment taught in that day evidences their relation to those men, that it is the father of all moral principle in them, and that they have a right to claim it as though they were blood of the blood, and flesh of the flesh of the men who wrote that Declaration, (loud and long continued applause) and so they are.
That is the electric cord in that Declaration that links the hearts of patriotic and liberty-loving men together, that will link those patriotic hearts as long as the love of freedom exists in the minds of men throughout the world. [Applause.]