I don’t think Federal Troops would attack fellow Americans. But you can be sure they’d be ordered to if any state attempted to seceded.
Possible, but I don’t think it likely in the case of a reasonably peaceable parting of the ways. I actually think that the left would be delighted to see some of the red states go it on their own. While I don’t consider myself a secesher, thanks to our scotus its well on its way to becoming a strategy openly discussed in polite company.
We don’t need to actually secede, just kick out of the union Boston, New York, Philadelphia, Detroit, Chicago, Madison, Miami, Seattle, San Fransisco, LA and Vermont.
Give the eastern cities to Canada and the ones on the west coast make dependent republics.
I really hope you are correct - but I keep thinking about the Civil War... They did then - do you really think people are any different today?