A bunch of states seceded from the British Union. They were successful. It's not something I would be bringing up at that time, but for whatever reason, nobody seems to have noticed the irony.
Those 'states' were not part and British Union. They were colonies. They had no representatives in London. They had absolutely no say in the policies of Parliament or the British Crown. Their complaints to the British Union were ignored. Their pleadings for just treatment were ignored. Read the Declaration... they listed their reasons and justifications, in detail.
It was not 'secession.' It was a Revolution against 'intolerable oppression.'
No comparison to what happened in 1860-61.