You forget that the push to abolish slavery began in England and Scotland with men like John Newton and William Wilberforce. Trade in slaves was abolished by the UK, enforced around the world by the Royal Navy beginning in 1807. The US followed suit effective January 1, 1808. Of course with 4 million slaves in the South, they had enough ‘breeding stock’ that new slaves were not needed for replenishment. Also, they did not want to risk a fight with the RN.
Slavery in the UK ended in 1833 but it took the deaths of almost a million Americans to end it in the US.
There’s about a 30 year difference between what Great Britain did and what the US did when it comes to ending the slave trade and slavery in general. Hardly makes a difference although Brits wrap themselves up in the Union Jack when squawking about their fight against the peculiar institution. They are only 30 years better than America and we lost close to one million men in ending it.