The problem with asking this question is that the US didn't just adopt slavery on it's own. When European powers colonized the Americas, they brought slavery with them and integrated it into the economies of their new settlements. That is a huge reason institutional racism has historically been such a big problem in America - it was deliberately established as a key part of colonial society for maximum imperialist exploitation. So the issue isn't so much how the USA could have not adopted slavery, but rather how Americans could have disowned it at the nation's founding or at the very least much earlier than 1865. In parts of America, this actually did happen. Inspired by the Revolution, northern states like Massachusetts acted to abolish slavery or like New York they gradually phased it out. This was in part because the North did not rely upon slavery for economic development, instead their economies were based off small farming, trade, and commerce. Slavery played a part in all of these elements, but not a necessary one. In contrast the South's economy was designed by Britain to be based primarily off industrial levels of tobacco and indigo farming which required brutal labor that no free man would do. Despite this, Southerners like Washington and Jefferson predicted that slavery would eventually die out on its own. Unfortunately they were wrong thanks to the cotton gin. To get the South to abolish slavery voluntarily and do so early, the cotton gin would need to be butterflied so that slavery would decline and cease to be profitable. Given this POD, slavery could almost certainly be abolished everywhere in America by 1840, only seven years after the British Empire. It's not a perfect scenario, but millions would be spared the evils of bondage, rape, and murder. And even if some minor rebellion did occur over slavery (likely confined to SC or the Deep South) America wouldn't have suffered the death and destruction of the Civil War.
Bottom line: if you want a completely slavery-free America you would need an altruistic Europe that doesn't partake in genocide or slavery when colonizing the Americas. If you want to get rid of slavery early (but after July 4, 1776), butterfly the cotton gin so slavery declines and the South is forced to industrialize. Alternatively, the South could refuse to ratify the Constitution and a war breaks out between North and South in 1788-89. If the North wins, it could result in the gradual abolition of slavery down the road. But given that there is a chance the South would win instead (and therefore be able to perpetuate slavery long after its OTL death of 1865) a peaceful abolition is preferable.