During both of his campaigns for the U.S. Presidency, Donald Trump regularly warned that the continuation of any number of processes he said were on-going during both the Obama and Biden administrations would result in us "not having a country anymore." In fact, that warning was among his favorite remarks--especially before or after hugging a flag.
On this view, a big influx of immigrants is said to threaten country loss. And other things do so as well: too much gender modification, too heavy a focus on diversity and equity in employment and/or education, a fiscal deficit that's said to be too high to safely maintain for much longer, too large expenditures on government services and too much dependence on those services by the populace. In addition, we were told we should worry about the popularity of religions other than Christianity, or of languages other than English. Perhaps too many vegetarians or homosexuals might also be suggested to bring about the decease of the good ole U. S. of A.
This attitude makes the United States an essentially White, Christian, meat-eating, English-speaking, heterosexual nation--and one in which learning about, or even thinking too much about any other ways of life is frowned upon. The idea put forth is that if we lose any of the enumerated essential qualities of America....ZOOP! we'll find ourselves living in a different country. [NB: I suppose the steady increase of winter temperatures, decrease of liveable summers, the slow disappearance of potable water, breatheable air, affordable houses, or port cities might also have been thought to be examples of country Kryptonite, but none of those ever seem to be mentioned by Republicans as being particularly worrisome.]
When considering this matter of what is essential to our country's identity, it should be remembered that there is no provision of the Constitution--either in its original version or subsequent to amendments--that would be violated by any of the scenarios of doom suggested by such campaign speeches. For example, given an ocean of incoming immigrants, failure to allow huge numbers of such new residents to vote might cause problems for the nation's democratic basis, and if electoral and other governmental activities are conducted solely in English, a large influx of non-English speakers could also be problematic. But there seem much simpler solutions to those concerns than those involving walls or armies. (Incidentally, I'm told that ICE is now among the largest armies in the world.)
On the other hand, if the Constitution is believed to be our country's founding and supporting document, failures to allow free speech, organization, assembly, or press could be inferred to be fatal. That document also clearly requires independent judicial and legislative branches, and if either of those should come to be nearly--or completely-- under the thumb of the executive branch, it might make sense to argue that our country has disappeared.
Unlike many current democracy scholars, I believe in the ultimacy of constituent power in self-governing polities. I don't know if there's ever a clear, bright line that a polity must cross for it "not to be the same country anymore." I suppose there generally is not any such line. But I do think it's clear that, if we are concerned about the continued existence of the nation that was divised by the U.S. Constitution (with all its faults--as my readers may know, I'm not its biggest fan), the norms that must be retained are not those that Trump has insisted Americans need to be distressed about. Quite the contrary: what is most worrisome is the destruction of those institutions and norms that are being intentionally "wood-chipped" by the exectutive branch right now.