America was NOT the first nation to abolish slavery. Not by any stretch of the imagination.
By 1783 a movement to abolish slavery had begun in England. John Graves Simcoe, Lieutenant-Governor of Upper Canada tabled the Act Against Slavery in 1793. Passed by the local Legislative Assembly, it was the first legislation to outlaw the slave trade in a part of the British Empire.
The British Slavery Abolition Act received Royal Assent in Britain in 1833.
France outlawed slavery in 1794.
Men and women of great moral courage throughout the world, including the fledgling US Republic, realized that the slave trade was an abomination and actively worked to end it.
However, the US was still fighting to the death about this in 1865. This is nearly a century after Britain began the process of abolition.
Sorry to break this news to you.