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 [the founders]. . . . If they look back through this history [of the revolution and founding] 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.]
Note that fully half the population was new to the country, yet no one was threatened thereby. What do you suppose we can learn from that?
UPDATE: As if to illustrate the point, ninme reports that an important Dutch patriot is moving to the US. Do go read because it's an important story in itself. But note the first comment on the post: "Welcome home Hirisi." America is not a culture, a tribe, a religion. It's a people dedicated to the proposition that all men are created equal, and that's why Ninme's reader instinctively understands that a Somali-born Dutch politician's true home is America.