Your skipping over the secession part.
Secession is, by itself, not a civil war. It’s more of a divorce. It generally becomes a war — though it’s arguable if it is a civil war — when the secedee tries to force the seceder back into the fold.
I don’t think it’s going to work out that way this time. New York might give the election to Hillary by 16 points but that’s still 40-something percent of men willing to fight. I think It will be intrastate Warfare because a half million people in Staten Island will fight here. as well many millions of others in Upstate New York. of course once you Southerners win back your state you are more than welcome to help