Portugal, Spain, France, Holland, Britain and Denmark brought African slaves to the New World long before there was a country called the United States.
The colonies declared independence from Great Britain in 1776 but Great Britain did not recognize the U.S. as a country until the matter was officially settled by the Treaty of Paris in 1783. 82 years later after our Civil War, the institution of slavery that was brought to the New World by the above named countries was abolished by the ratification of the 13th amendment. Brazil didn't outlaw slavery until 1888. In the big picture of slavery in the New World, the area that would become the U.S. was not one of the big players. Brazil was the largest importer by far.
So what to the slave is the Fourth of July? It marked the dawn of an era that would see the end of slavery in the United States. Slavery that still exists in many parts of the world.
Country / Destination Slaves Delivered
Brazil - 4,000,000
Spanish Empire - 2,500,000
British West Indies - 2,000,000
French West Indies - 1,600,000
British North America & U.S. - 500,000
Dutch West Indies - 500,000
Danish West Indies - 28,000
Europe - 200,000
Total 11,328,000
http://www.slaverysite.com/Body/facts and figures.htm