This is an unfortunate and erroneous view of history. If you read the Federalist papers you will know the founders deeply struggled with slavery. They could not help the world as it was in 1783. They were incorporating the first republic in 1,000 years so defacto almost all "white" people were subject to either a monarch or tribal leader in 1783. They were not slaves but their liberty and freedom was severely restricted. Yes slavery took too long to be abolished in the United States, but when it was finally decided that it would be, 600,000 to 850,000 died to make it so. That was 2 to 3% of the US population.
The facts are quite different. If your "Howard Zinn" view of history was correct, blacks and native Americans would not have been able to own slaves which they did.