People are inconsistent. America is inconsistent. The United States is inconsistent.
Get over it.
People have a duality of nature. They want freedom. They want security. The battle between these mutually exclusive natures creates conflict and conflict is sometimes violent.
We could drive around in tanks and make the speed limit 5mph and no one inside a vehicle would ever be killed in an automotive accident. Pedestrians and buildings might suffer though, tanks have a lousy field of view.
Both freedom and security or safety are subjective ideologies based on perspective.
Some people think guns are dangerous. I don't. I see guns as being machines. Machines are as dangerous as the operator who uses them. Drop a bunch of ball bearings on the ground and then run a lawn mower over them and we have something very dangerous. Run a lawnmower over a gravel driveway and "blam".
Subjective opinions, and some objective opinions, are capable of being swayed through the use of propaganda.
Was the United States a place where millions fought against slavery or was the United States a place where people were enslaved?
Both actually. There was slavery in Brazil, Venezuela and Argentina. These places didn't fight wars against slavery. Is the United States on higher or lower moral ground?
I don't think the United States is morally superior or morally inferior.
The United States is a democracy that changes as public opinion changes.
When farming in the Americas was primarily large plantations slaves were needed because there was no mechanization and there were no itinerant agricultural workers. Labor was needed to plant and harvest these large plantations. Slaves were being sold in Africa. Labor was needed. Slaves were purchased and put to work in the Americas.
During the mid 1800's the industrial revolution, family farm and a population large enough to support itinerant agricultural labor developed. Slavery was no longer an answer, the cost of slaves became an economic problem. In the United States we fought a war against slavery. In other American nations slavery withered away economically without the costs of a war.
Most of the people in the United States hated slavery so much they were not willing to allow it to wither away naturally the way it had in other places and the way it did in other American nations.
People in the United States hated slavery so much they fought a war to destroy it.
Was it stupid to fight a war? Are Blacks in other American nations better off than Blacks in the United States?
(Personally I find the discussion of race to be racist, but, racism exists and if we don't discuss it openly in the light it breeds like mold in the dark)