I can't say with certainty that slavery would have ended more quickly and more completely if the South had been allowed to leave and escaped former slaves had been allowed to remain free, and the North and the rest of the world had been a positive influence on the South. However, it's certainly a possibility that it would have ended sooner if the southern slave owners had agreed to a system of compensated emancipation and freed the slaves without a war and without secession, as most nations that ended slavery did. That absolutely would have been preferable to the Civil War as it happened.

California, like anywhere else on Earth, should have the right to secede whether the United States likes it or not. The preferences of the other 49 states and Washington DC is not relevant. That was the position of the United States government on Yugoslavia and other places around the world but not on Ukraine. However, morality and the law as I understand it are that any people should have the right to leave, just as explained in the initial words of the US Declaration of Independence.

The United States has been becoming worse year after year after year for decades, and it's guaranteed to continue down that path if we don't change something.

Climate change is so unimaginable that most Americans deny it's happening.

I can't say with certainty that slavery would have ended more quickly and more completely if the South had been allowed to leave and escaped former slaves had been allowed to remain free, and the North and the rest of the world had been a positive influence on the South. However, it's certainly a possibility that it would have ended sooner if the southern slave owners had agreed to a system of compensated emancipation and freed the slaves without a war and without secession, as most nations that ended slavery did. That absolutely would have been preferable to the Civil War as it happened.

I think the election of Donald Trump, if you want to call it an election, was unimaginable to most people, which is part of how it happened.

Slavery remained in the Deep South by other names - in prison programs with charges over nothing and eternal debt that threatened every African-American in the South right up through World War II. And that was after killing three-quarters of a million people, destroying cities, and creating hostility that exists to this day over the the Confederate flag and the racism it symbolizes, all brewing out of bitterness over a war that didn't have to happen.