The US Pledge of Allegiance to the Flag pretty much conflates the USA as "one Nation" and "the Republic." They're different.
If you believe the US is primarily "a (White) Christian nation" — with "White," when said or thought, possibly limited to "Aryan" and "Christian" traditionally referring to a set of Protestants — then a major potential or actual threat to the US is substantial immigration, since large-scale immigration would undermine and "impurify" our "one Nation."
If the US is primarily the Republic, foreign meddling in an election is an attack on a crucial democratic part of our republicanism and a crisis-level threat.
WORDS MEAN, and a crucial part of politics is our conscious, semiconscious, and unconscious disputes over what we mean by key terms.
My oath was to "preserve, protect, and defend the Constitution of the United States" and the Republic in which it is embodied. And I wouldn't be a member of a Christian America and perhaps not a White one. Others have strong loyalty to America as a culture and identity, a loyalty I understand and in some ways share. Still others have a loyalty to Americanism rooted in soil and confirmed in at least two senses by blood: they can be enemies of the Republic.