Most contemporary Nation-states exist as the result of the post-WWII order (i.e. most of Eurasia), or liberated colonies in the Western Hemisphere and Global South. Taken in this sense, America is simply one of the latter...

But I think the post-cold-war, post-9/11 wars America of today faces a severe existential crisis from which I'm not sure if there's a way back.

Perhaps a better question than "what makes America America?" is "What is America for?" For 3 generations, there has been a clear answer to that question. "Uphold the post-WWII global order", "Defeat Communism," "Defeat Terrorism", etc...

Without that kind of mandate, I think we have to face the fact that like an African nation consisting of myriad tribes that have nothing to do with one another that were "thrown together" by an external colonizing force, America consists of a bunch of different "micronations" that really don't want anything to do with one another.