I agree - but the potential for Civil War has been looming in the US since the 1960s when the Democrats and Republicans started to become polarised around Christianity and around the issues of abortion in particular, and the separation of Church and State. Their previous Civil War was about slavery and was about whether the two countries (north & south) could co-exist. They could... but it was tentative. We're seeing the same polarisation as happened in the 1850s.

I remember the Yugoslav war because I'm British and because my father was working with the British military at the time. I don't know the complexities of an already complex situation but I do remember it being absolute horrific at every level and dominating the news cycle day-after-day.

Americans do indeed all identify as Americans, but at the moment that is about all they have in common. The Civil War won't break out because there is a nation state within another nation state, it'll break out because the whole thing is a tinder box and there are two very distinct groups attempting to define what 'American' means. It's like two strangers living in the same house eyeballing each other because they both believe they a) own the house and b) should be allowed to arrange the furniture the way they want. The vast majority of US citizens won't want a Civil War, but they may get dragged into one anyway.