As someone who lives in New England, what happens in Georgia, Virginia or Tennessee, or the fact that they’re in the same country as me has essentially no effect on my life, and I imagine that was even more so the car back then, when travel and communication was much slower. If anything, if a person was opposed to the politics of the southern states, their exit from the union would be advantageous as they’d no longer be contributing electoral votes, congressmen and senators for “the opposite side.” In 1860 the United States was a new nation whose borders were constantly changing so I can’t imagine that there would be that strong of a nationalistic attachment to the shape of the country as it was, in the way that part of the identity of France is l’Hexagone. I understand that there were radical abolitionists throughout the country who were happy to fight and die to end slavery but these John Brown/Bleeding Kansas types were definitely a minority inspired by a particular sort of Christianity. So, minding that, was there any significant opposition to the war in the north, as in “I don’t care if the South stays or leaves, or even if I do care enough to prefer that they stay, the maintenance of the union is not something I’m willing to die for, nor is it worth my son or brother or husband or friends or neighbors dying for.”
I feel like that’s a different sort of thing than the Irish draft riots, which were more along the lines of “we just got here, this isn’t our war” nor am I talking about northerners who opposed the war because they were sympathetic to the southern cause and supported the continuation of slavery.
The humorously applicable username u/secessionisillegal outlines the arguments for (and against) "peaceable separation" for both the north and south here:
Probably first and foremost on their mind (given their username) is that secession simply isn't an option in the United States of America. What was to stop ANY state from threatening secession every time they didn't get their way? The idea undermines the authority of the federal government.
On the Southern side the secession would probably not be as clean as they would like. California was considering splitting off entirely (and if the USA didn't have authority to keep them in the new CSA would have even less). What about Texas, who less than 20 years prior had already been its own country?
On the Northern side a significant number of problems would still simply continue to exist but now be even more complicated to deal with. They'd need treaties over the use of the major rivers like the Mississippi, treaties about runaway slaves, treaties about trade, tariffs, etc. The types of things that may just very well lead to war later anyways.
What about the national debt? Did the CSA expect to cleanly separate from that peacefully? The USA would certainly negotiate otherwise, and did the CSA expect to have the economic output alone to deal with that?
Even for proponents of a peaceful separation there were significant logistical issues as you can see.
While more can always be said, there's plenty in our VFAQ on this:
There was immense opposition to the war in the North, especially if you include those states that were still part of the USA but were slave states with mixed identities as Northern and Southern. There was a genuine and deliberate political agenda with powerful adherents and serious political influence, which sometimes considered and (in the case of a few fringe radicals) actually plotted armed resistance to the Lincoln government.
It's instructive to look at the presidential election of 1864. The Democratic Party was bitterly split on the question of war vs. peace. The Peace Democrats, known as Copperheads, were buoyed by the poor showing of Union forces in the war, and managed to seize control of the convention to the extent of writing the party platform. This platform duly labeled the war a failure and called for peace to be made at the earliest opportunity. Although it was not clear exactly what the terms of this peace should be, it ought to have been obvious in 1864 that the South would not negotiate on the basis of its return to the Union.
However, the Democrats' actual candidate for president, George McClellan, came from the War Democrats faction of the party, and once he was nominated, found himself in the awkward position of being forced to run on a platform that its detractors quickly and successfully began to portray as a peace-at-any-price demand. McClellan therefore found himself a war candidate running on a peace platform, and accepted the nomination but not the platform, causing the peace faction no small distress and resentment.
It would not be fair to say that all Peace Democrats were Copperheads. Some of them (Prominently including governor Seymour of New York) wanted to negotiate a deal that would allow the south back into the United States and guarantee that slavery would not be meddled with, but would not have countenanced a peace based on allowing the Confederacy its independence. To further complicate matters, as the war started to go better for the Union forces, and even after it was actually won, some powerful backers of peace at any price made efforts to seem as though they had never said any such thing at all.
The Democratic campaign was thus marked by confusion and infighting, especially since Lincoln's running mate was Andrew Johnson, a War Democrat, while McClellan's running mate was a prominent Copperhead. But to your question, the point is that there was a peace faction that came very close to seizing control of one of the two major parties.