The US would have remained part of England. Your sentiment is also baloney because at the time the constitution was written, almost all the states were still slave states. They had had 11 years to pass abolition laws, yet they were all still slave states. Massachusetts was only a "free" state because of judicial activism and a ridiculous interpretation of the state's new constitution by a liberal activist court.
Your belief is based on largely the same bankrupt propaganda as what the progressives push.
The automatic assumption on part of progressives is that a slave owner is automatically destined to be pro slavery. That may have been the case in most of the world for centuries, but that wasn't the case in America.
The abolition if slavery necessarily required sabotage of slavery on part of slave owners otherwise not a single one of those states that became free states would've become free states. In other words there would've been no North to participate in the Civil War you constantly re-litigate.
"They had had 11 years to pass abolition laws, yet they were all still slave states."
They had a lot more than 11 years, and Massachusetts wasn't the only state that became a free state, and states like Vermont and those in the Northwest came into the Union freesoil-on-day-one because of Jefferson's abolitionist ordinance.
The Northern abolitionists were dead on to hold Jefferson in high regard. Unlike school kids today, there's a high probability that school kids in the 1820s may well have read the full text of the Northwest Ordinance as a matter of course. They would've held the original source material in their fingers.