I'd go farther than that.
Had the South seceded in 1850, it would have been successful. The railroad network in the 1860s was just barely extensive enough to support the logistics of invading the South. Also the disproportion in industrial power and population was a lot less. War would have ended in fairly short order with the North recognizing it couldn't defeat the South.
In 1870, OTOH, the disproportion would have been much greater, and the war would have ended more quickly with a Union victory.
IMO, the war was fought during the only period when we could have had a long, bloody war. YMMV
Sherman,
Let me apologize publicly. My last post to you has hostile and undeserved when I re-read your initial comments.
Please blame it on male menopause and too much scotch in a hillbilly Scots-Irishman.
Your comments are sound. Arguable, but sound.