You mean this map?
I see battles in Union Maryland, Pennsylvania, Ohio, Indiana, West Virginia, Kentucky, Missouri, Nebraska, Oklahoma & New Mexico, among others.
If you count up the battles here, you'll see that during the war's first 12 months, more were fought in Union states & territories than Confederate and more Confederate soldiers died in the Union than in the Confederacy.
It's simply a lie to claim that Confederates posed no "existential threat" to the United States.
Can/could 5 million whites, over half women and children ever pose and extensional threat to 30+ million northerners? Show me one Southern CONTEMPORARY writing, legislation, letter, editorial stating the the South wanted to conquer the North? You sir are a ridiculous a$$. You have a cartoon mind.