The American Revolution was as much about slavery (keeping it, not ending it) as anything else. I realized that as a young man back in the 1970's when I came across the Somersett Case*, a ruling by Lord Mansfield in England in 1772. Slavery could not exist on English soil, according to English law. Hence a Virginia slave who set foot on English soil became free. This led a bunch of slave owners in Virginia to set up their Committees of Correspondence to join in the independence movement started in Boston for other reasons.
Most Americans still have not heard of the Somersett case, but at least among academic historians the Mansfield ruling is better known, though of course many are still in denial about its role in motivating Washington, Jefferson and their crew.
I only recently learned (from How the Scots Invented the Modern World
by Arthur Herman, published in 2001) about a case ruling in Scotland (part of Great Britain, but with a separate legal system). In the year following the Declaration of Independence, 1777, Lord Kames and colleagues ruled that an African-born man, Joseph Knight, who had been a slave in Jamaica (then a British colony; sugar grown by slaves was a major source of British wealth) was free once he was brought to Scotland. The court wrote "The dominion assumed over the negro, under the law of Jamaica, being unjust, could not be supported in this country to any extent."
It is important to distinguish between the Somersett ruling and the Knight ruling, although they both resulted in slaves being set free. Lord Mansfield made his ruling as a point of law: slavery (serfdom) had been abolished in English law. Since there was no basis in law for slavery, a slave coming from the Americas or elsewhere became free in England.
The Scottish notion was more radical. Due to work already done by Lord Kames and others, the judges believed that slavery was against nature and human nature. They believed that any law allowing for slavery was itself invalid. They prized justice and liberty over mere legal precedence and rulings by parliaments and kings.
Sadly, rather than learning from the Knight ruling (which the many lawyers who led the independence movement in the U.S. would have known about), the new ruling class in the former colonies allowed slavery to continue. When the U.S. Constitution was written, they wrote slavery into it.
Which leads us to the question of racism. Ethnic groups belief in their own superiority goes back to pre-history, but modern racism is a modern phenomena, and it was developed in the United States. Slavery was a product of greed and the use of force. Once the slaves became an essential part of the economy of the U.S., and of the owned wealth of the southern aristocracy, there was a an incentive to keep slavery in place. The flowery words of the Declaration of Independence and the Bill of Rights of the new Constitution indicated that the Enlightenment doctrines of liberty and equality were well known in the U.S.
To keep the slave system intact a new doctrine, an aristocrats' trump card, was needed. That was the inferiority of non-white humans; racial inferiority. In fact, the racist theory of southerners for the most part denied that Africans were human. They were at best sub-human. Hence they could not have human rights. Hence the reasoning of the Knight case could not apply in the U.S. Hence slaves were property, a theory confirmed by the U.S. Supreme Court in the Dred Scott Decision.
All the evidence to the contrary did not matter. It is important to keep in mind that when people have an economic interest at stake, they can become purposefully blind to questions or justice or even of factual reality.
The Democratic Party was founded explicitly as a racist, pro-Slavery party by the slave trader and eventually President Andrew Jackson and his friends. The party did not truly reject racist doctrines until after Lyndon Johnson became President in 1964.
After the Civil War and the anti-slavery amendments to the U.S. Constitution the myth of racial inferiority continued to damage people and society. Segregation of the races was substituted for liberty and equality.
When we celebrate Martin Luther King day it is important not to forget that many, many people fought to end slavery and racism. It was a process that started long before the American Revolution. It had many heroes and heroines, but in the long run what mattered was changing the hearts and minds of the vast majority of Americans.
The Somersett and Knight cases should be added to the texts on civics and history used in American public schools. As far as I know this has not happened, and it shows how false patriotism and phony history still misshape our society.
*not a consistent spelling; also mentioned as Somerset and Sommersett in texts and law books.