National identity is a collection of things that contribute to culture, like food, language, customary observances. It's always evolving because people add to it, and things disappear from it over time. Tex-Mex food didnt always exist, it was an evolution of the merging of National customs. Spanglish didnt always exist, but it's a thing in many places in the US. In fact our "English" is hardly so, and depending on the region of the Country you're in, it can be indecipherable, because it has remnants of other languages in it. Hell the South is fighting for their right to "preserve heritage" of traitors.
Let me give you an idea of the founding principals of this Country in its inception:
"This new world hath been the asylum for the persecuted lovers of civil and religious liberty from every part of Europe, hither have they fled, not from the tender embraces of the mother, but from the cruelty of the monster; and it is so far true of England, that the same tyranny which drove the first emigrants from home, pursues their descendants still." - Thomas Paine
Paine, who was considered by Jefferson to be the best writer of the Revolutionary era, always maintained that the American plight is not loyalty to some Motherland, but is instead a kinship of any people fleeing oppression. He was also the guy who said this:
"He that would make his own liberty secure must guard even his enemy from oppression; for if he violates this duty he establishes a precedent that will reach to himself."